Heterobimetallic catalysts and site-differentiated ligands for preparation thereof

ABSTRACT

Phosphine phosphonate and phenoxyphosphine ligands bearing polyethylene glycol (PEG) chains are used as described herein to produce heterobimetallic catalysts. The ligands can be metallated selectively with palladium or nickel and secondary metal ions to provide well-defined heterobimetallic compounds. These heterobimetallic complexes exhibit accelerated reaction rates and greater thermal stability in olefin polymerization compared to other catalysts.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/693,524, filed Jul. 3, 2018, entitled “Heterobimetallic Catalystsand Site-Differentiated Ligands for Preparation Thereof,” and U.S.Provisional Patent Application No. 62/807,831, filed Feb. 20, 2019,entitled “Heterobimetallic Catalysts and Site-Differentiated Ligands forPreparation Thereof,” and the contents of both applications areincorporated by reference herein.

This invention was made with government support under Grant No.CHE-1750411 awarded by the National Science Foundation. The Governmenthas certain rights in the invention.

BACKGROUND

This disclosure pertains to heterobimetallic catalysts and the synthesisthereof.

To meet the diverse needs of the global materials market, a wide varietyof polyolefins are desired. Greater than 70% of the world'sethylene-based polymers are manufactured using transition metalcatalyzed processes. Because the intrinsic properties of polyolefins aredetermined by how their building blocks are assembled, having a broadassortment of metal catalysts to synthesize polyolefins is required. Thedevelopment of customized catalysts to access specific polymer productsis a major scientific endeavor. Traditionally, altering a molecularcatalyst's steric bulk or electronic structure requires syntheticmodification of its ligand framework, which can be cumbersome andlabor-intensive. To be industrially useful, the metal catalysts mustalso be highly active, tolerant of trace impurities, and compatible athigh reactor temperatures (e.g. >80° C.).

The discovery that cationic late transition metal diimine complexes arecapable of copolymerizing ethylene with methyl acrylate inspired manyresearchers to search for new families of polar group compatiblemolecular catalysts. Late transition metal complexes are widelyinvestigated as olefin polymerization catalysts because they have betterfunctional monomer compatibility and greater tolerance of polarimpurities/solvents compared to early transition metal complexes. Forexample, the development of neutral palladium phosphine sulfonatecomplexes by Drent et. al. has enabled the copolymerization of ethylenewith difficult to incorporate polar monomers such as vinyl acetate,vinyl halide, acrylonitrile, and acrylamide. Most recently, the researchgroups of Nozaki and Jordan disclosed that cationic palladium compoundsligated by P,O-ligands also gave active copolymerization catalysts. Amajor drawback in many of these metal-based systems, however, is thatthe presence of polar monomers causes a significant decrease incatalytic activity compared to in the presence of just ethylene.Furthermore, the molecular weights of the copolymers also tend to be low(M_(n)<10⁵). An extensive assortment of nickel catalysts with diverseethylene polymerization behaviour has also been reported. Some of theircommon limitations, however, are that they can exhibit low catalystactivity, produce short chain oligomers/polymers, and have poor controlover polymer microstructures. These shortcomings have thus preventedlate transition metal complexes from being viable catalysts forcommercial polyolefin synthesis.

SUMMARY

The present disclosure relates generally to heterobimetallic catalystcompounds and new strategies to enhance the capabilities of latetransition metal olefin polymerization catalysts. In particular, thepresent disclosure describes the construction of a site-differentiateddinucleating platform for the self-assembly of a novel family ofpalladium-metal and nickel-metal complexes, where metal can be elementsof the s-block, d-block, or f-block in the periodic table. The thermallyrobust heterobimetallic catalysts are particularly useful for olefinhomo- and copolymerization.

The strategies described herein overcome the deficiencies ofconventional olefin polymerization catalysts. They provide a simple andversatile method to fine tune transition metal catalysts with minimalsynthetic effort. The pairing of secondary metal ions with palladium ornickel phosphine-phosphonate complexes imparts greater reactivity andthermal stability to the parent catalyst in both ethylene homo- andcopolymerization. An important feature is the installation of twopolyethylene glycol (PEG) chains to the ligand's phosphonate group,which provides a well-defined binding site for alkali ions to yielddiscrete heterobimetallic species in solution.

These heterobimetallic compounds exhibit superior catalytic performancein ethylene homopolymerization and ethylene/polar olefincopolymerization compared to conventional catalysts. Time dependentpolymerization studies indicate that the complexes display uniquely longcatalyst lifetimes at 100° C., and can even operate at temperatures ashigh as 140° C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general structure for preferred embodiments ofheterobimetallic complexes described herein.

FIG. 2 shows a synthetic scheme, Scheme 1, for the synthesis of ligandsand palladium complexes, in accordance with preferred embodimentsdescribed herein.

FIG. 3 shows examples of preferred embodiments of heterobimetalliccomplexes.

FIG. 4 shows steps in the procedure for preparing(2-bromophenyl)bis(2-methoxyphenyl)phosphine.

FIG. 5 shows a schematic for the binding of palladium complexes withmetal ions, in accordance with preferred embodiments described herein.

FIG. 6 shows job plots of alkali ion binding behavior for arepresentative palladium complex and various alkali ions, in accordancewith preferred embodiments described herein.

FIG. 7 shows a comparison of the turnover frequencies (TOFs) ofexemplary catalysts in ethylene homopolymerization at varioustemperatures.

FIG. 8 shows the X-ray structure of a representative complex (4b) inaccordance with preferred embodiments described herein.

FIG. 9 shows the X-ray structure of a representative complex (4b-Na) inaccordance with preferred embodiments described herein.

FIG. 10 shows the X-ray structure of a representative complex (5b) inaccordance with preferred embodiments described herein.

FIG. 11 shows a synthetic scheme, Scheme 2, for the synthesis of nickelphenoxyphosphine complexes, in accordance with preferred embodimentsdescribed herein.

FIG. 12 shows steps in the synthesis of a reference complex Ni10.

FIG. 13 shows steps in the synthesis of a reference complex Ni11.

FIG. 14 shows steps in the synthesis of an intermediate compound.

FIG. 15 shows UV-vis absorbance spectra of the addition of NaBAr^(F) ₄to Ni11.

FIG. 16 is a Job Plot showing the coordination interactions betweencomplex Ni11 and NaBAr^(F) ₄.

FIG. 17A shows the X-ray structure of a representative complex Ni11-Na,in accordance with preferred embodiments described herein.

FIG. 17B shows the X-ray structure of a reference complex Ni11.

FIG. 18A is a plot showing reaction temperatures and polymer yieldsduring the course of a 60 min run by the Ni11-Na complex at 100 μMcatalyst concentration.

FIG. 18B is a plot showing reaction temperatures and polymer yieldsduring the course of a 60 min run by the Ni11-Na complex using a 50 μMcatalyst concentration.

FIG. 19 shows a synthetic scheme, Scheme 3, for the synthesis of ligandsuseful for forming heterobimetallic complexes, in accordance withpreferred embodiments described herein.

FIG. 20 shows a synthetic scheme, Scheme 4, for the synthesis ofheterobimetallic complexes, in accordance with preferred embodimentsdescribed herein.

FIG. 21 shows job plots of binding behavior for representative nickelcomplexes with NaBAr^(F) ₄ in CDCl₃.

FIG. 22 shows a job plot of binding behavior for a representative nickelcomplex with Zn(OTf)₂ in CD₃CN.

FIG. 23 shows a comparison of the activities of representative catalystswith different metal ions in tetrahydrofuran solvent.

FIG. 24 shows a comparison of the activities of representative catalystswith different polar monomers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure relates to heterobimetallic catalysts and methodsfor synthesis thereof. In particular, the present disclosure relates tonovel phosphine phosphonate and phenoxyphosphine ligands bearingpolyethylene glycol (PEG) chains. These ligands can be metallatedselectively with palladium or nickel and secondary metal ions to providewell-defined heterobimetallic compounds. These heterobimetalliccomplexes exhibit accelerated reaction rates and greater thermalstability in olefin polymerization compared to their monopalladium ormononickel counterparts. The general ligand design strategy could alsobe extended to other classes of catalysts to boost their catalyticperformance.

The common feature of the heterobimetallic catalysts is that theycontain a primary metal site where polymerization takes place and asecondary metal site where substrates can interact (or serve otherancillary functions). The secondary metal binding site is designed tohave broad metal ion specificity so that a wide variety of mixed metalcomplexes could be generated easily. Polymerization results show thatthe presence of secondary metal ions can significantly impact catalystactivity, thermal stability, and polymer microstructure. This approachis better than existing technologies because a wide variety of polymertypes can be synthesized using a single universal catalyst platform.

In certain preferred embodiments, the heterobimetallic catalysts have astructure as shown below:

where M₁ is nickel or palladium and M₂ is any metal of the s-block,d-block, or f-block in the periodic table, such as any alkali, alkaline,transition, or rare earth metal. C₁ is a first chelator moiety selectedfrom:

where Ar specifies aromatic groups with different substituents, such asalkyl, phenyl, and alkoxy, X specifies different electron donating andwithdrawing substituents, such as alkoxy, amino, nitro, cyano, and otherfunctional groups, and R specifies alkyl or aryl groups, such as methyl,isopropyl, and phenyl. C₂ is a second chelator moiety selected from:

In C₂, Ar, R, and X are defined as above and n specifies the number ofrepeating units, which can vary from 0 to 4. Further, L refers to theligand donor groups such as phosphine, alkoxide, phosphine oxide, ether,amine, or carboxylate. The curved lines that connect the donors Lrepresent the organic linkers that make up the complete ligandstructure. The wavy lines show attachment points where Chelator 1 andChelator 2 could be covalently attached to one another. These preferredembodiments are also shown in FIG. 1.

In certain additional preferred embodiments, palladium-alkali catalystshave one of the structures shown below:

wherein Ar is Ph or (2-MeO)Ph, wherein Ph is a phenyl group, and whereinM is Li, Na, or K.

Preferred embodiments of palladium phosphine-phosphonate complexes wereobtained through the synthetic sequence shown in Scheme 1, in FIG. 2.Lithiation of (2-bromophenyl)diarylphosphine, followed by reaction withmethyldiglycol chlorophosphate, provided ligands 3a (Ar=phenyl) and 3b(2-methoxyphenyl) in moderate yields. Metallation of these ligands bytreatment with Pd(COD)(Me)(Cl) (COD=1,5-cyclooctadiene) gave complexes4a and 4b, respectively. Finally, chloride abstraction using AgSbF6 andpyridine furnished complexes 5a/5b. Single crystals of compounds 4b and5b were analyzed by X-ray crystallography (see Example 5 below and FIGS.8 and 10, respectively). In both structures, the palladium center issquare planar and the methyl group is trans to the phosphonate moiety.The bond metrics at the palladium core in 5b are similar to those in theanalogous diethylphosphonate variant reported by Jordan and coworkers.

Additional preferred embodiments of heterobimetallic complexes are shownin FIG. 3. In the preferred embodiments shown in FIG. 3, as well as allpreferred embodiments of heterobimetallic complexes described herein, Phis phenyl, PPh₃ is phosphine (PH₃), and Ar specifies aromatic groupswith different substituents, such as alkyl, phenyl, and alkoxy. Xspecifies different electron donating and withdrawing substituents, suchas alkoxy, amino, nitro, cyano, and other functional groups. R specifiesalkyl or aryl groups, such as methyl, isopropyl, and phenyl. Inaddition, the polyethylene glycol chains can vary in length, preferablyhaving 2-4 ethylene glycol units. The overall charges of theheterobimetallic complexes are determined by the oxidation states of themetal ions used and could impact their structural stability and chemicalreactivity.

When nickel phenoxyimine or palladium phosphine phosphate estercatalysts are paired with secondary Lewis acids, their reactivity issignificantly increased and/or altered. The presence of alkali ions canalso dramatically accelerate the ethylene polymerization rates of nickelphenoxyphosphine catalysts. Because these reactions generate such largeexotherms, careful reaction temperature control is required to achievethe best catalytic performance.

In certain additional preferred embodiments, nickel-alkali catalystshave the structure shown below:

wherein Ph is a phenyl group, M is Li, Na, or K, and wherein Me₃P istrimethylphosphine. In additional preferred embodiments, M is Na and thecatalysts are nickel-sodium phenoxyphosphine complexes. The nickelphenoxyphosphine complexes feature PEG side arms and can chelatesecondary alkali ions. The corresponding nickel-sodium complexes areextraordinarily active catalysts for ethylene polymerization,demonstrating again that using secondary Lewis acids to boost catalyticperformance is applicable to many different catalyst systems.

To enable the incorporation of pendant alkali ions to nickelphenoxyphosphine complexes, in preferred embodiments, polyethyleneglycol (PEG) chains are attached to the ortho position of the phenolatering, as shown generally in Scheme 2 in FIG. 11 and discussed more fullyin Example 6 below.

The pairing of alkali ions with late transition metal complexes leads tosignificant catalyst enhancements, which is consistent with studies ofan analogous palladium system. Polymerization was carried out usingthese catalysts in the polar organic solvent THF. Upon the addition ofexternal Lewis such as Zn²⁺ or Co²⁺, the nickel phosphine phosphonatePEG complexes could generate heterobimetallic species that are moreactive than their parent complexes. By using THF as solvent, thesecondary metal scope was expanded, which allowed for the use ofdifferent metal-metal combinations. The efficient copolymerization ofethylene with several polar monomers was readily achieved with theseheterobimetallic complexes in THF. This appears to be the first time ithas been reported that copolymerization can be performed in polarsolvent with activity up to 10⁴ g/mol Ni·h.

Additional preferred embodiments include a method for preparingheterobimetallic catalysts, comprising reacting a compound having astructure of:

wherein A is Pd or Ni, Ph is phenyl, and B and C are independentlyselected from CH₃, Cl, pyridine, phenyl, PPh₃, wherein PPh₃ isphosphine, and PMe₃, wherein PMe₃ is trimethylphosphine, with a metalsalt, wherein the metal salt comprises any metal of the s-block,d-block, or f-block in the periodic table, such as any alkali, alkaline,transition, or rare earth metal, to form a heterobimetallic catalyst.

Additional preferred embodiments include heterobimetallic catalystsprepared by complexing the structures shown below:

wherein Ar is a phenyl group, with a metal salt, where the metal saltcan be an alkali salt such as a salt of Ca²⁺ or Mg²⁺ or a transitionmetal salt such as a salt of Co²⁺ or Zn²⁺.

In the preferred embodiments and examples included herein, the compoundnumbering schemes used in (1) Scheme 1, FIGS. 2-10, and Examples 1-5,(2) Scheme 2, FIGS. 11-18, and Examples 6-9, and (3) Schemes 3-4, FIGS.19-24, and Examples 10-12 are all distinct and do not overlap. Forexample, complexes 5a and 5b found in Scheme 1, FIG. 2, and Examples 1and 4-5 have different structures relative to compound 5 found in Scheme2, FIG. 11, and Example 6.

EXAMPLE 1. PALLADIUM-ALKALI CATALYSTS

Commercial reagents were used as received. All air- and water-sensitivemanipulations were performed using standard Schlenk techniques or undera nitrogen atmosphere using a glovebox. Anhydrous solvents were obtainedfrom an Innovative Technology solvent drying system saturated withArgon. High-purity polymer grade ethylene was obtained from MathesonTriGas without further purification. The compounds(2-bromophenyl)diphenyl phosphine and Pd(COD)(Me)(Cl) were preparedaccording to literature procedures.

NMR spectra were acquired using JOEL spectrometers (ECA-400, 500, and600) and referenced using residual solvent peaks. All ¹³C NMR spectrawere proton decoupled. ³¹P NMR spectra were referenced to phosphoricacid. For polymer characterization: ¹H NMR spectroscopy—Each NMR samplecontained ˜20 mg of polymer in 0.5 mL of 1,1,2,2-tetrachloroethane-d₂(TCE-d₂) and was recorded on a 500 MHz spectrometer using standardacquisition parameters at 120° C. ¹³C NMR spectroscopy—Each NMR samplecontained ˜50 mg of polymer and 50 mM (8.7 mg) chromium acetylacetonateCr(acac)₃ in 0.5 mL of TCE-d₂ and was recorded at 120° C. (125 MHz). Thesamples were acquired using a 90° pulse of 11.7 μs, a relaxation delayof 4 s, an acquisition time of 0.81 s, and inverse gated decoupling. Thesamples were preheated for 30 mM prior to data acquisition. The carbonspectra were assigned based on the chemical shift values reported in theliterature. High-resolution mass spectra were obtained from the massspectral facility at the University of Houston. Elemental analyses wereperformed by Atlantic Microlab.

Gel permeation chromatography (GPC) data were obtained using a Malvernhigh temperature GPC instrument equipped with refractive index,viscometer, and light scattering detectors at 150° C. with1,2,4-trichlorobenzene (stabilized with 125 ppm BHT) as the mobilephase. A calibration curve was established using polystyrene standards.

Preparation of (2-bromophenyl)bis(2-methoxyphenyl)phosphine. See FIG. 4.The following two step procedure was used: Step 1. A 100 mL Schlenkflask was charged with magnesium turnings (0.6 g, 25 mmol, 2.5 equiv.)under N₂ in 20 mL of THF. The compound 2-bromoanisole (2.6 mL, 20 mmol,2.0 equiv.) was added and the mixture was stirred at room temperaturefor 1 h until the solution turned brown. The resulting Grignard reagentwas cannula transferred to a THF solution containing PCl₃ (0.8 mL, 10mmol, 1.0 equiv.) at −78° C. After the addition was complete, thesuspension was stirred at room temperature for another 30 min. Thissolution was used directly in the next step. ³¹P NMR (CDCl₃, 243 MHz): δ(ppm)=62.49. Step 2. The compound 1,2-dibromobenzene (1.1 mL, 9.1 mmol,1.0 equiv.) was combined with 20 mL of Et₂O/THF (1:1). The solution wascooled to −110° C. using an cold bath containing Et₂O/Acetone/Pentane(85:10:5) and liquid N₂. A solution of n-butyllithium (1.6 M) (5.8 mL,9.2 mmol, 1.0 equiv.) was added slowly via syringe, taking care that thesolution flowed down from the wall of the flask rather than directlyinto the reaction mixture. The mixture turned slightly yellow and wasstirred for 30 mins at −110° C. The crude PAr₂Cl solution from step 1was precooled to −78° C. and then added to the reaction flask viasyringe. This final mixture was allowed to continue stirring at −110° C.for 10 mins and then slowly warmed up to −90° C. Saturated NH₄Clsolution (15 mL) was added to quench the reaction. The reaction mixturewas extracted into DCM (3×50 mL). The organic extracts were combined,dried over sodium sulfate, filtered, and then evaporated to dryness. Thecrude material was purified by silica gel column chromatography(hexanes/DCM, 1:1). A white solid (2.93 g, 7.3 mmol, 80%) was collectedas the final product. The NMR spectra of this compound match those thatwere reported previously.

Preparation of 1:

Phosphorus trichloride (0.54 mL, 6.2 mmol, 1.0 equiv.) was added slowlyto a Et₂O solution (50 mL) containing diethylene glycol monomethyl ether(1.87 g, 15.5 mmol, 2.5 equiv.) and pyridine (1.0 mL, 12.5 mmol, 2.0equiv.) that was immersed in an ice bath. After complete addition, thereaction mixture was allowed to warm up to room temperature and stirredfor 16 h. The white pyridinium chloride suspension was removed by vacuumfiltration, and was washed twice with Et₂O (2×50 mL). The filtrates werecombined and concentrated under reduced pressure and dried under vacuumto yield a clear oil (1.82 g, 6.3 mmol, 100%). The crude product wasused directly in the next step without further purification. ¹H NMR(CDCl₃, 600 MHz): δ (ppm)=6.93 (d, ¹J_(PH)=716.4 Hz, 1H), 4.28-4.15 (m,4H), 3.69 (m, 4H), 3.63 (m, 4H), 3.53 (m, 4H), 3.35 (s, 6H). ¹³C NMR(CDCl₃, 150 MHz): δ (ppm)=71.98, 70.58, 70.28 (d, J_(PC)=5.85 Hz), 64.74(d, J_(PC)=5.85 Hz), 59.15. ³¹P NMR (CDCl₃, 243 MHz): δ (ppm)=9.95.

Preparation of 2:

To a stirred acetonitrile solution (5 mL, dry) of trichloroisocyanuricacid (TCICA) (0.48 g, 2.1 mmol, 1.0 equiv.) at room temperature wasadded a solution of 1 (1.78 g, 6.2 mmol, 3.0 equiv.) in acetonitrile (5mL). The resulting mixture was stirred at room temperature. As thereaction proceeded, precipitation of cyanuric acid was observed. After30 min, the reaction flask was brought inside drybox for workup. Theheterogeneous mixture was filtered to remove the precipitate and thefiltrate was dried under vacuum to yield a clear liquid (1.75 g, 5.5mmol, 88%). This material was used without further purification. ¹H NMR(CDCl₃, 500 MHz): δ (ppm)=4.33 (m, 4H), 3.76 (m, 4H), 3.66 (m, 4H), 3.54(m, 4H), 3.37 (s, 6H). ¹³C NMR (CDCl₃, 100 MHz): δ (ppm)=71.97, 70.79,69.52 (d, J_(PC)=8.8 Hz), 68.53 (d, J_(PC)=6.8 Hz), 59.21. ³¹P NMR(CDCl₃, 202 MHz): δ (ppm)=5.84.

Preparation of 3a:

A 100 mL Schlenk flask was charged with (2-bromophenyl)diphenylphosphine (1.0 g, 2.94 mmol, 1.0 equiv.) in 30 mL of THF. The flask wascooled to −78° C., and a solution of n-butyllithium (1.6 M) (2.0 mL,3.20 mmol, 1.1 equiv.) was added via syringe, giving a deep yellowsolution. After stirring for 20 min, a solution of 2 (0.95 g, 2.95 mmol,1.0 equiv.) in THF (5 mL) was added by syringe, which turned thesolution pale orange. After stirring for 40 min, the cold bath wasremoved, and the flask was allowed to warm up to room temperatureovernight while stirring. The reaction mixture was then concentratedunder reduced pressure to afford an orange oil. The crude product waspurified by silica gel column chromatography (100% ethyl acetate toremove mobile impurities, followed by ethyl acetate/chloroform/methanol(10:1:1) to elute the product) to yield a slightly yellow oil (0.85 g,1.56 mmol, 53%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=8.11 (m, 1H), 7.41 (m,2H), 7.31 (m, 6H), 7.22 (m, 4H), 7.14 (m, 1H), 4.24-4.04 (m, 4H),3.54-3.44 (m, 12H), 3.34 (s, 6H). ¹³C NMR (CDCl₃, 100 MHz): δ(ppm)=145.27, 141.60 (m), 137.52 (d, J_(PC)=9.8 Hz), 135.91 (d,J_(PC)=12.7 Hz), 134.94 (m), 134.56, 133.72 (d, J_(PC)=15.7 Hz), 133.41(d, J_(PC)=17.6 Hz), 132.26 (d, J_(PC)=20 Hz), 128.54 (m), 71.92, 70.42,70.10 (d, J_(PC)=4.9 Hz), 64.98 (d, J_(PC)=4.9 Hz), 59.13. (Note: Thesignals in the aromatic region could not be assigned due to overlappingpeaks); ³P NMR (CDCl₃, 162 MHz): δ (ppm)=19.19, −8.72. ESI-MS(+) calc.for C₂₈H₃₆O₇P₂[M+K]⁺=585.15730, found 585.17930.

Preparation of 3b:

A 100 mL Schlenk flask was charged with(2-bromophenyl)bis(2-methoxyphenyl) phosphine (0.66 g, 1.65 mmol, 1.0equiv.) in 30 mL of THF. The flask was cooled to −78° C., and a solutionof n-butyllithium (1.6 M) (1.1 mL, 1.76 mmol, 1.1 equiv.) was added viasyringe, giving a deep yellow solution that was stirred for 20 min Afterstirring for 20 min, a solution of 2 (0.53 g, 1.65 mmol, 1.0 equiv.) inTHF (5 mL) was added by syringe, which turned the solution pale orange.After stirring for 40 min, the cold bath was removed, and the flask wasallowed to warm up to room temperature overnight while stirring. Thereaction mixture was then concentrated under reduced pressure to affordan orange oil. The crude product was purified by silica gel columnchromatography (100% ethyl acetate to remove mobile impurities, followedby ethyl acetate/chloroform/methanol (10:1:1) to elute the product) toyield a slightly yellow oil (0.60 g, 0.99 mmol, 60%). ¹H NMR (CDCl₃, 500MHz): δ (ppm)=8.14 (dddd, J_(PH)=13.5 Hz, J_(HH)=7.6 Hz, J_(PH)=3.5 Hz,J_(HH)=1.5 Hz, 1H), 7.39 (td, J_(HH)=7.5 Hz, J_(PH)=3.5 Hz, 1H), 7.34(tt, J_(HH)=7.5 Hz, J_(PH)=J_(HH)=1.5 Hz, 1H), 7.29 (t, J_(HH)=7.5 Hz,2H), 7.04 (m, 1H), 6.83 (dd, J_(HH)=8 Hz, J_(PH)=5 Hz, 2H), 6.79 (t,J_(HH)=7.5 Hz, 2H), 6.54 (br s, 2H), 4.23-4.05 (m, 4H), 3.66 (s, 6H),3.52-3.44 (m, 12H), 3.32 (s, 6H). ¹³C NMR (CDCl₃, 125 MHz): δ(ppm)=161.05 (d, J_(PC)=16 Hz), 141.83 (dd, J_(PC)=24.5, 12.8 Hz),135.48 (d, J_(PC)=14.8 Hz), 134.76 (dd, J_(PC)=11.0, 8.6 Hz), 133.85,133.82 (dd, J_(PC)=187, 34 Hz), 132.04 (d, J_(PC)=2.4 Hz), 130.04,128.24 (d, J_(PC)=14.6 Hz), 125.55 (d, J_(PC)=14.6 Hz), 120.95, 110.18,71.94, 70.40, 69.99 (d, J_(PC)=6.1 Hz), 64.82 (dd, J_(PC)=6.1, 2.4 Hz),59.10, 55.61. ³¹P NMR (CDCl₃, 162 MHz): δ (ppm)=19.48, −27.25. ESI-MS(+)calc. for C₃₀H₄₀O₉P₂[M+H]⁺=607.2226, found 607.2235.

Preparation of 4a:

Inside the drybox, compound 3a (117 mg, 0.21 mmol, 1.0 equiv.) andPd(COD)(Me)(Cl) (57 mg, 0.21 mmol, 1.0 equiv.) were combined in a smallvial and then dissolved in DCM (5 mL) at room temperature. The reactionmixture was stirred at room temperature for 1 h and then filteredthrough a pipet plug. The filtrate was dried under vacuum. Pentane wasadded to the residue and stirred until a white solid formed (125 mg,0.18 mmol, 83%). ¹H NMR (CDCl₃, 600 MHz): δ (ppm)=7.98 (dd, J_(PH)=5.2Hz, J_(HH)=2.0 Hz), 7.55-7.38 (m, 12H), 7.12 (m, 1H), 4.17-4.10 (m, 4H),3.55-3.44 (m, 12H), 3.31 (s, 6H), 0.69 (d, J_(PH)=2.4 Hz, 3H). ¹³C NMR(CDCl₃, 100 MHz): δ (ppm)=136.62 (m), 134.83 (m), 134.45 (d, J_(PC)=12.7Hz), 133.16 (m), 132.79 (m), 131.21, 130.76 (d, J_(PC)=13.2 Hz), 129.63,129.13, 128.88 (d, J_(PC)=10.7 Hz), 71.87, 70.35, 69.82 (d, J_(PC)=6.8Hz), 66.82 (d, J_(PC)=5.8 Hz), 59.13, 0.93. (Note: The signals in thearomatic region could not be assigned due to overlapping peaks); ³¹P NMR(CDCl₃, 162 MHz): δ (ppm)=32.15 (d, J_(PP)=13 Hz), 20.76 (d, J_(PP)=13Hz). Anal. Calc. for C₂₉H₃₉ClO₇P₂Pd: C, 49.52; H, 5.59. Found: C,49.34;H, 5.55.

Preparation of 4b:

Inside the drybox, compound 3b (165 mg, 0.27 mmol, 1.0 equiv.) andPd(COD)(Me)(Cl) (72 mg, 0.27 mmol, 1.0 equiv.) were combined in a smallvial and then dissolved in DCM (5 mL) at room temperature. The reactionmixture was stirred at room temperature for 1 h and then filteredthrough a pipet plug. The filtrate was dried under vacuum and washedwith Et₂O to form a white solid (185 mg, 0.24 mmol, 89%). ¹H NMR (CDCl₃,600 MHz): δ (ppm)=7.88 (m, 1H), 7.51-7.46 (m, 3H), 7.41 (t, J_(HH)=7.2Hz, 1H), 7.34 (br s, 1H), 7.29-7.25 (m, 2H), 6.95 (t, J_(HH)=7.2 Hz,2H), 6.91 (dd, J_(HH)=8.4 Hz, J_(PH)=4.8 Hz, 2H), 4.22-4.07 (m, 4H),3.64 (s, 6H), 3.61-3.46 (m, 12H), 3.34 (s, 6H), 0.57 (d, J_(PH)=3 Hz,3H). ¹³C NMR (CDCl₃, 125 MHz): δ (ppm)=160.72 (d, J_(PC)3.8 Hz), 136.52,136.50 (dd, J_(PC)=34.9, 10.7 Hz), 134.50 (d, J_(PC)=15.9 Hz), 134.10(t, J_(PC)=6.4 Hz), 133.30, 131.45 (dd, J_(PC)=6.1, 2.5 Hz), 130.26 (dd,J_(PC)=185.8, 17.1 Hz), 129.82 (d, J_(PC)=13.5 Hz), 120.92 (d,J_(PC)=9.8 Hz), 116.14 (d, J_(PC)=51.4 Hz), 111.23 (d, J_(PC)=5.0 Hz),71.87, 70.35, 70.03 (d, J_(PC)=7.4 Hz), 66.54 (d, J_(PC)=6.1 Hz), 59.11,55.47, −0.22. ³¹P NMR (CDCl₃, 243 MHz): δ (ppm)=23.39 (d, J_(PP)=8.3Hz), 21.51 (d, J_(PP)=8.2 Hz). Anal. Calc. for C₃₁H₄₃ClO₉P₂Pd: C, 48.77;H, 5.68. Found: C, 48.75; H, 5.85.

Preparation of 5a:

Inside the drybox, 4a (76 mg, 0.11 mmol, 1.0 equiv.) and AgSbF₆ (37 mg,0.11 mmol, 1.0 equiv.) was combined in a small vial. A solution of DCM(5 mL) and pyridine (0.1 mL) was added at room temperature and thereaction mixture was stirred for 1 h. The mixture was then filteredthrough a pipet plug and the filtrate was dried under vacuum. A solutionof Et₂O was added to wash the residue to give a sticky oil (86 mg, 0.09mmol, 81%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=8.71 (d, J_(HH)=4.8 Hz,2H), 8.13 (m, 1H), 7.93 (m, 1H), 7.67-7.47 (m, 14H), 7.15 (m, 1H), 4.07(m, 4H), 3.54-3.39 (m, 12H), 3.32 (s, 6H), 0.58 (d, J_(PH)=3.2 Hz, 3H).δ (ppm)=¹³C NMR (CDCl₃, 100 MHz): δ (ppm)=150.11, 139.26, 135.44 (m),134.99 (m), 134.35 (d, J_(PC)=9.9 Hz), 133.41 (m), 131.97, 131.60,131.49 (m), 129.39 (d, J_(PC)=8.8 Hz), 128.29, 127.86, 125.86, 71.76,70.25, 69.34 (d, J_(PC)=5.9 Hz), 67.39 (d, J_(PC)=5.8 Hz), 59.01, 3.95.(Note: The signals in the aromatic region could not be assigned due tooverlapping peaks); ³¹P NMR (CDCl₃, 243 MHz): δ (ppm)=33.11 (d,J_(PP)=19.4 Hz), 21.01 (d, J_(PP)=19.4 Hz).

Preparation of 5b:

Inside the drybox, 4b (155 mg, 0.20 mmol, 1.0 equiv.) and AgSbF₆ (70 mg,0.20 mmol, 1.0 equiv.) was combined in a small vial. A solution of DCM(10 mL) and pyridine (0.1 mL) was added at room temperature and thereaction mixture was stirred for 1 h. The mixture was then filteredthrough a pipet plug and the filtrate was dried under vacuum. A solutionof Et₂O was added to wash the residue to give a sticky oil (201 mg, 0.19mmol, 95%). ¹H NMR (CDCl₃, 600 MHz): δ (ppm)=8.67 (d, J_(HH)=3.6 Hz,2H), 7.97 (m, 1H), 7.92 (t, J_(HH)=7.2 Hz, 1H), 7.58-7.56 (m, 5H), 7.51(t, 7.8 Hz, 1H), 7.43-7.31 (m, 3H), 7.05 (t, J_(HH)=7.8 Hz, 2H), 6.99(dd, J_(HH)=8.4 Hz, J_(HH)=4.8 Hz, 2H), 4.00-3.87 (m, 4H), 3.68 (s, 6H),3.54-3.42 (m, 12H), 3.32 (s, 6H), 0.39 (d, J_(PH)=3.6 Hz, 3H). ¹³C NMR(CDCl₃, 100 MHz): δ (ppm)=160.70 (d, J_(PC)=2.9 Hz), 150.15, 139.02,136.80 (d, J_(PC)=11.7 Hz), 135.03 (d, J_(PC)=16.5 Hz), 134.62 (dd,J_(PC)=26.2, 3.6 Hz), 134.36, 134.05 (t, J_(PC)=8.3 Hz), 132.15 (d,J_(PC)=16 Hz), 130.52 (d, J_(PC)=14.5 Hz), 128.95 (dd, J_(PC)=187.6,17.6 Hz), 125.70, 121.27 (d, J_(PC)=11.6 Hz), 114.49 (d, J_(PC)=56 Hz),111.73, 71.77, 70.28, 69.42 (d, J_(PC)=5.8 Hz), 66.84 (d, J_(PC)=6.8Hz), 59.02, 55.56, 3.19. ³¹P NMR (CDCl₃, 243 MHz): δ (ppm)=23.93 (d,J_(PP)=14.3 Hz), 21.54 (d, J_(PP)=14.3 Hz).

Preparation of 6b:

Inside the drybox, the palladium phosphine-diethyl phosphonate complexes(115 mg, 0.19 mmol, 1.0 equiv.) and AgSbF₆ (65 mg, 0.19 mmol, 1.0equiv.) were combined in a small vial. A solution of DCM (10 mL) andpyridine (0.1 mL) was added at room temperature and the reaction mixturewas stirred for 1 h. The mixture was then filtered through a pipet plugand the filtrate was dried under vacuum. A solution of Et₂O was added towash the residue to give a white solid (149 mg, 0.17 mmol, 89%). ¹H NMR(CDCl₃, 600 MHz): δ (ppm)=8.66 (d, J_(HH)=4.9 Hz, 2H), 7.93 (t, 7.8 Hz,1H), 7.83 (m, 1H), 7.62-7.53 (m, 6H), 7.38-7.34 (m, 3H), 7.05 (t,J_(HH)=7.5 Hz, 2H), 6.99 (dd, J_(HH)=8.4 Hz, J_(HH)=4.8 Hz, 2H), 3.87(m, 4H), 3.68 (s, 6H), 1.10 (t, J_(HH)=7.0 Hz, 6H), 0.38 (d, J_(PH)=3.0Hz, 3H). ¹³C NMR (CDCl₃, 100 MHz): δ (ppm)=160.66 (d, J_(PC)=2.2 Hz),150.11, 139.14, 136.81 (d, J_(PC)=11.3 Hz), 135.24 (d, J_(PC)=14.1 Hz),134.80 (dd. J_(PC)=46.7, 11.4 Hz) 134.36, 133.42 (dd, J_(PC)=9.3, 8.2Hz), 132.11 (d, J_(PC)=7.0 Hz), 130.63 (d, J_(PC)=12.2 Hz), 129.18 (dd,J_(PC)=184.7, 17.5 Hz) 125.74, 121.24 (d, J_(PC)=11.3 Hz), 114.49 (d,J_(PC)=56 Hz), 111.73 (d, J_(PC)=4.4 Hz), 64.44 (d, J_(PC)=6.4 Hz),55.58, 15.89 (d, J_(PC)=6.5 Hz), 3.12. ³¹P NMR (CDCl₃, 243 MHz): δ(ppm)=24.11 (d, J_(PP)=14.1 Hz), 21.08 (d, J_(PP)=14.1 Hz).

EXAMPLE 2. SOLUTION STUDIES

To investigate the interactions of the PEGylated palladium compoundswith alkali ions, solution studies were carried out. The method ofcontinuous variation (Job Plot analysis) was used to determine thebinding stoichiometry of the current palladium complexes with alkaliions, as generally shown in FIG. 5. To perform these experiments, stocksolutions of 4a (6 mM, 6 mL) and MBAr^(F) ₄ (6 mM, 15 equiv. Et₂O tosolubilize the salts, 6 mL, M=Li⁺, Na⁺, or K⁺) were prepared separatelyin CDCl₃. Various amounts of each stock solution were added to an NMRtube so that a total volume of 1 mL was obtained. Ten different NMRsamples were prepared, each containing a different ratio of 4a:M. Thesamples were recorded at room temperature by ¹H NMR spectroscopy. TheNMR spectra of 4a in the presence of various amounts of MBAr^(F) ₄ salts(M=Li⁺, Na⁺, or K⁺, BAr^(F) ₄=tetrakis(3,5-trifluoromethylphenyl)borate)were recorded. The two hydrogen resonances centered at ˜4.1 ppmcorresponding to the C1 methylene unit of the PEG chains in 4a (labeledas H_(a) in FIG. 4) shift in the presence of alkali ions. The chemicalshift separation between H_(a1) and H_(a2) increases as the Pd molefraction decreases. The changes in the ¹H NMR signals of H_(a) as afunction of the mole fraction of 4a are provided in Tables 1-3 below.

TABLE 1 NMR Job plot data for 4a + LiBAr^(F) ⁴ _(a) [4a]/([4a] +(Δδ)[4a]/([4a] + 4a (mL) Li⁺(mL) [Li⁺]) δ(ppm)^(b) Δδ(ppm) [Li⁺]) 1 0 14.136 0 0 0.9 0.1 0.9 4.131 0.005 0.0045 0.8 0.2 0.8 4.123 0.013 0.01040.7 0.3 0.7 4.116 0.020 0.014 0.6 0.4 0.6 4.106 0.030 0.018 0.5 0.5 0.54.094 0.042 0.021 0.4 0.6 0.4 4.094 0.042 0.0168 0.3 0.7 0.3 4.089 0.0470.0141 0.2 0.8 0.2 4.089 0.047 0.0094 0.1 0.9 0.1 4.089 0.047 0.0047 0 10 — — 0 ^(a)Concentrations of stock solutions: [4a] = 6 mM in CDCl₃,[Li⁺] = 6 mM in CDCl₃/Et₂O.

TABLE 2 NMR Job plot data for 4a + NaBAr^(F) ⁴ _(a) [4a]/([4a] +(Δδ)[4a]/([4a] + 4a (mL) Na⁺(mL) [Na⁺]) δ(ppm)^(b) Δδ(ppm) [Na⁺]) 1 0 14.132 0 0 0.9 0.1 0.9 4.117 0.015 0.0135 0.8 0.2 0.8 4.088 0.044 0.03520.7 0.3 0.7 4.056 0.076 0.0532 0.6 0.4 0.6 4.011 0.121 0.0726 0.5 0.50.5 3.948 0.184 0.092 0.4 0.6 0.4 3.936 0.196 0.0784 0.3 0.7 0.3 3.9370.195 0.0585 0.2 0.8 0.2 3.943 0.189 0.0378 0.1 0.9 0.1 3.946 0.1860.0186 0 1 0 — — 0 ^(a)Concentrations of stock solutions: [4a] = 6 mM inCDCl₃, [Na⁺] = 6 mM in CDCl₃/Et₂O.

TABLE 3 NMR Job plot data for 4a + KBAr^(F) ⁴ _(a) [4a]/([4a] +(Δδ)[4a]/([4a] + 4a (mL) K⁺(mL) [K⁺]) δ(ppm)^(b) Δδ(ppm) [K⁺]) 1 0 14.132 0 0 0.9 0.1 0.9 4.125 0.007 0.0063 0.8 0.2 0.8 4.098 0.034 0.02720.7 0.3 0.7 4.075 0.057 0.0399 0.6 0.4 0.6 4.015 0.117 0.0702 0.5 0.50.5 3.974 0.158 0.079 0.4 0.6 0.4 3.951 0.181 0.0724 0.3 0.7 0.3 3.9440.188 0.0564 0.2 0.8 0.2 3.942 0.19 0.038 0.1 0.9 0.1 3.942 0.19 0.019 01 0 — — 0 ^(a)Concentrations of stock solutions: [4a] = 6 mM in CDCl₃,[K⁺] = 6 mM in CDCl₃/Et₂O.

The changes in the chemical shifts of the methylene hydrogen atoms of 4aat ˜4.1 ppm were used to construct Job plots. FIG. 6 shows job plots forcomplex 4a with MBAr^(F) ₄ (M=Li⁺, Na⁺, K) in CDCl₃. The totalconcentration of 4a/MBAr^(F) ₄ was 6 mM for all data points and X_(Pd)was defined as [4a]/([4a]+[M⁺]). The peak maxima of the Job plots for4a/M⁺ all occur at X_(Pd)=0.5, which indicates that a 1:1 stoichiometryis optimal between complex 4a and alkali ions. The slopes of the threeplots suggest that the alkali ion affinity of 4a follows the orderNa⁺˜K⁺>Li⁺. The dinuclear structure of the palladium-sodium complex4b-Na was confirmed by X-ray crystallographic analysis (see Example 5below and FIG. 9). The structure revealed that the palladium center in4b-Na has the expected square planar geometry, with slightly modifiedbond distances compared to those in 4b (Pd—O and Pd—Cl are longerwhereas Pd—P and Pd—C are shorter). The sodium ion is six-coordinate dueto ligation by five oxygen donors and a bridging chloride. For complex5b, which contains a pyridine donor instead of chloride like in 4b,similar alkali ion binding behavior was observed. Complex 6b, which lackPEG chains, appeared to bind Na⁺ only weakly as indicated by minorshifts in its NMR spectra.

EXAMPLE 3. CYCLIC VOLTAMMETRY

To probe the electronic impact of M⁺ on the palladium complexes, cyclicvoltammetry measurements were conducted. Due to solubilityconsiderations and the highly negative reduction potential of thecompounds, THF was used as the electrochemical solvent. In the absenceof M⁺, 4a displayed a cathodic peak at −2.5 V (vs.ferrocene/ferrocenium), which was tentatively assigned to reduction ofthe Pd(II) center. The cyclic voltammograms of 4a-Li, 4a-Na, and 4a-Kshowed additional broad irreversible waves at approximately −2.2, −2.3,and −2.40 V, respectively, and were attributed to Pd-centered reductionprocesses in the heterobimetallic species. This trend is consistent withthe electronegativity of the alkali ions, which would be expected tocause a decrease in the electron density at the palladium core throughelectronic induction. It is believed that in THF, an appreciable amountof both monopalladium 4a and heterobimetallic 4a-M species are presentat equilibrium due to the lower alkali ion binding affinity of 4a incoordinating solvents compared to in non-coordinating solvents (e.g.chloroform).

EXAMPLE 4. POLYMERIZATION STUDIES

Palladium phosphine-phosphonate-PEG complexes were tested as catalystsfor ethylene homopolymerization. Inside the drybox, the palladiumcomplexes (5 μmol) and alkali salts (5 μmol) were dissolved in 10 mL oftoluene/DCM (8:2) and stirred for 10 mins. The mixture was sealed insidea vial using a rubber septum and brought outside of the drybox. Under anatmosphere of N₂, the catalyst solution was loaded into a syringe. Toprepare the polymerization reactor, 40 mL of dry toluene was added to anempty autoclave and preheated to the desired temperature. The autoclavewas purged with ethylene (20 psi) for 1 min and then the catalystsolution was injected into the autoclave via syringe. The reactorpressure was increased to 400 psi of ethylene and the contents werestirred vigorously for 2 h. To stop the polymerization, the autoclavewas vented and cooled in an ice bath. A solution of MeOH (100-200 mL)was added to precipitate the polymer. The polymer was collected byvacuum filtration, rinsed with MeOH, and dried under vacuum at 80° C.overnight.

Results are shown in Table 4 below.

TABLE 4 Ethylene Homopolymerization Data^(a) TOF (×10³ M_(n) ^(b) M_(w)/Entry Cat. Salt g/mol · h) (×10³) M_(n) ^(b) 1 5a none 0 — — 2 5a Na⁺ 0— — 3 5b none 233 2.17 1.27 4 5b Li⁺ 615 2.15 1.65 5 5b Na⁺ 675 2.901.46 6 5b K⁺ 467 2.90 1.50 7 6b none 395 1.66 1.48 ^(a)Polymerizationconditions: Pd catalyst (5 μmol), MBAr^(F) ⁴ (5 μmol, if any), ethylene(400 psi), 2 mL DCM, 48 mL toluene, 2 h at 80° C. ^(b)Determined by GPCin trichlorobenzene at 140° C.

At 80° C. in toluene under 400 psi of ethylene, complex 5a wascompletely inactive (entry 1) whereas complex 5b displayed moderateactivity (entry 3, TOF=233×10³ g/mol Pd·h). The poor reactivity of 5awas most likely due to the insufficient steric protection of thepalladium center, which is typically required to help promote chaingrowth over chain termination. In comparison, the Jordan-type catalyst6b yielded polyethylene with a TOF of 395×10³ g/mol Pd·h under the samereaction conditions (entry 7). In all cases, the polymers produced werehighly linear and the molecular weight is low (M_(n)=˜1.66-2.17×10³),which is consistent with other reported Pd(P, O-ligand) systems. Thelower TOF of 5b compared to that of 6b suggest that the free PEG chainsin the former might be self-inhibiting.

Next, the effects of alkali salts on ethylene polymerization wereevaluated, with the results also shown in Table 4 above. Using the samepolymerizations conditions as above, it was observed that the reactionof 5b and MBAr^(F) ₄ (1:1) with ethylene led to catalytic rateenhancements of about 2.6×, 2.9×, and 2.0× for Li⁺ (entry 4), Na⁺ (entry5), and K⁺ (entry 6), respectively, compared to 5b. Interestingly, thepolymer molecular weight and polydispersity remained relatively constantin both the presence and absence of alkali ions. The polymerizationrates increase in the order Na⁺>Li⁺>K⁺ was somewhat surprising becauseit was observed previously that potassium ions had a more beneficialeffect on nickel phenoxyimine-PEG catalysts than lithium ions. In thepresent system, it was hypothesized that a combination of two differentfactors account for the “heterobimetallic effect”—the electronegativity(i.e. Li⁺>Na⁺>K⁺) and the association constant (i.e. Na⁺˜K⁺>Li⁺) of thesecondary cations. Interestingly, the reaction of 6b and NaBAr^(F) ₄(1:1) with ethylene also led to rate enhancements (see Table 5 below,compare entry 9 vs. 13), although the alkali ion effect is diminished athigh temperatures (vide infra). Further mechanistic studies are neededto understand the origins of this heterobimetallic phenomenon.

TABLE 5 Temperature Study of 5b, 5b-Na, 6b, and 6b-Na in EthyleneHomopolymerization.^(a) TOF Temp. (×10³ M_(n) ^(b) Entry Complex Salt (°C.) g/mol · h) (×10³) M_(w)/M_(n) ^(b) 1 5b None 80 233 2.17 1.27 2 5bNone 100 737 — — 3 5b None 120 451 — — 4 5b None 140 85 — — 5 5b Na⁺ 80597 — — 6 5b Na⁺ 100 2716 1.27 2.10 7 5b Na⁺ 120 1586 0.98 1.74 8 5b Na⁺140 1065 1.27 1.36 9 6b None 80 364 — — 10 6b None 100 1395 1.14 1.61 116b None 120 999 1.14 1.32 12 6b None 140 32 — — 13 6b Na⁺ 80 890 — — 146b Na⁺ 100 2040 — — 15 6b Na⁺ 120 1140 — — 16 6b Na⁺ 140 585 — —^(a)Polymerization conditions: Pd catalyst (10 μmol), MBAr^(F) ₄ (10μmol, if any), ethylene (400 psi), 2 mL DCM, 48 mL mesitylene, 1 h.^(b)Determined by GPC in trichlorobenzene at 140° C.

To determine the optimal reaction temperature, several catalysts werescreened in ethylene polymerization from 80 to 140° C. inmesitylene/dichloromethane (24:1) for 1 h. FIG. 7 shows a comparison ofthe turnover frequencies (TOFs) of catalysts 5b, 5b-Na, and 6b inethylene homopolymerization at various temperatures. For the compounds5b, 5b-Na, and 6b, reactions at 100° C. afforded the highest activityand their relative TOFs were generally observed in the order5b-Na>6b>5b. Remarkably, the heterobimetallic complex 5b-Na showed highactivity at 140° C. (TOF=1,065×10³ g/mol Pd·h), whereas both 5b and 6bwere considerably less active. Although the addition of NaBAr^(F) ₄ to6b also led to significant rate acceleration (Table 5 above), theheterobimetallic 5b-Na was still superior at temperatures greater than80° C. For example, at 140° C., the catalyst 5b-Na was ˜1.8× more activethan 6b-Na. These results suggest that having PEG chains in the ligand'sphosphonate framework helps to maintain its heterobimetallic core athigh temperatures.

To examine the catalyst lifetimes, time-dependent polymerizations werecarried out for both complexes 5b-Na and 6b at 100° C. (Table 6, below).

TABLE 6 Time Study for Complexes 5b-Na and 6b in EthyleneHomopolymerization.^(a) TOF(×10³ g/mol · h) Complex 15 min 30 min 60 min5b-Na 2528 2562 2726 6b 1351 1282 1395 ^(a)Polymerization conditions: Pdcatalyst (10 μmol), MBAr^(F) ⁴ (10 μmol, if any), ethylene (400 psi), 2mL DCM, 48 mL mesitylene, at 100° C.

During the period from 15-60 min, both catalysts maintained theircatalytic performance. However, 5b-Na showed about a ˜1.9× greaterturnover frequency (average=2,605×10³ g/mol Pd·h) than 6b(average=1,342×10³ g/mol Pd·h). The extraordinary thermal robustness ofthe 5b-Na complex is exciting from an industrial standpoint because mostlarge-scale commercial solution polymerizations are conducted at 140° C.or above. In fact, molecular catalysts that can operate within thistemperature regime are rare.

The palladium catalysts were also tested in ethylene and methyl acrylate(MA) copolymerization. Inside the drybox, the palladium complexes (10μmol) and alkali salts (10 μmol) were dissolved in 2 mL of DCM andstirred for 10 mins. The mixture was sealed inside a vial using a rubberseptum and brought outside of the drybox. Under an atmosphere of N₂, thealkyl acrylate comonomer was add into the catalyst solution and thefinal mixture was loaded into a syringe. To prepare the polymerizationreactor, 39-41 mL of dry toluene or mesitylene was added to an emptyautoclave and preheated to the desired temperature. The autoclave waspurged with ethylene (20 psi) for 1 min and then the catalyst solutionwas injected into the autoclave via syringe. The reactor pressure wasincreased to 400 psi of ethylene and the contents were stirredvigorously for 2 h. To stop the polymerization, the autoclave was ventedand cooled in an ice bath. A solution of MeOH (100-200 mL) was added toprecipitate the polymer. The polymer was collected by vacuum filtration,rinsed with MeOH, and dried under vacuum at 80° C. overnight. Theresults are shown in Table 7 below.

TABLE 7 Ethylene and Methyl Acrylate (Ma) Copolymerization by 5b^(a) TOFSalt (×10³ Inc.^(b) M_(n) ^(c) M_(w)/ Entry (equiv.) g/mol · h) (%)(×10³) M_(n) ^(c) 1 none 34 1.4 1.15 1.67 2 Li⁺(1.0) 76 1.5 1.63 2.00 3Na⁺(1.0) 63 1.5 1.73 2.17 4 Na⁺(5.0) 90 1.4 3.15 1.24 5 K⁺(1.0) 61 1.31.99 2.00 ^(a)Polymerization conditions: Pd catalyst (10 μmol), MBAr^(F)⁴ (10 μmol, if any), ethylene (400 psi), methyl acrylate (1.5M) in 50 mLtotal solution volume, 2 h at 80° C. ^(b)Determined by 1H NMRspectroscopy. ^(c)Determined by GPC in trichlorobenzene at 140° C.

The reaction of 5b with ethylene/MA at 80° C. afforded linearpoly(ethylene-co-methyl acrylate) containing ˜1.4 mol % of in-chainpolar groups (entry 1). Under the same conditions, the 5b-M complexesalso yielded copolymers with similar molecular weights and MA content as5b. Once again, the heterobimetallic catalysts exhibited greatercatalytic activity than the monopalladium catalysts. The highest TOF wasachieved using 5b/NaBAr^(F) ₄ (1:5), which is about a 2.6× improvementover that of 5b (compare entry 1 vs. 4). A slight increase in thecopolymer M_(n) was also obtained in the presence of sodium ions(M_(n)=3.15×10³ for 5b-Na vs. 1.15×10³ for 5b).

To investigate the copolymerization behavior of the catalysts at hightemperatures, MA was replaced with tert-butyl acrylate (BA) as the polarmonomer. Results are shown in Table 8 below.

TABLE 8 Ethylene and Tert-Butyl Acrylate (BA) Copolymerization Data for5b and 6b.^(a) TOF Salt (×10³ Inc.^(c) M_(n) ^(d) Entry (equiv.) g/mol ·h) (%) (×10³) M_(w)/M_(n) ^(d) 1 none 56 0.8 1.58 1.49 2 none 70 1.21.04 1.64 3 none 43 1.6 1.43 1.28 4 none  0 — — — 5 Li⁺(1.0) 52 0.9 1.662.00 6 Na⁺(1.0) 51 0.9 1.76 2.23 7 Na⁺(5.0) 64 0.8 2.34 1.55 8 Na⁺(1.0)84 1.2 2.30 1.47 9 Na⁺(1.0) 69 1.9 2.48 1.56 10 Na⁺(5.0) 72 1.7 2.141.41 11 Na⁺(1.0) 63 1.3 1.73 1.55 12 none 78 1.0 0.99 2.16 13 none 481.7 1.03 1.93 ^(a)Polymerization conditions: catalyst (10 μmol),MBAr^(F) ⁴ (10 μmol, if any), ethylene (400 psi), 39-41 mL mesitylene, 2h. cDetermined by ¹H NMR spectroscopy. ^(d)Determined by GPC intrichlorobenzene at 140° C.

In general, it was observed that the percentage of BA incorporation intothe copolymer was enhanced either by elevating the reaction temperatureor increasing the starting BA concentration. Although the addition ofsodium salts to 5b led to modest increases in catalyst activity andmolecular weight under certain conditions (e.g. compare entry 2 vs. 8),its most pronounced effect was on the catalyst's thermal stability. Forexample, at 120° C., the TOF of 5b-Na was 63×10³ g/mol Pd·h (entry 11)whereas that of 5b was negligible (entry 4). Importantly, all of thepoly(ethylene-co-tert-butyl acrylate) obtained showed relatively narrowM_(w)/M_(n) (1.28-2.23), which suggest that the catalysts aresingle-site species.

EXAMPLE 5. X-RAY DATA

Single crystals suitable for X-ray diffraction studies were picked outof the crystallization vials and mounted onto Mitogen loops usingParatone oil. The crystals were collected at a 6.0 cm detector distanceat −150° C. on a Brucker Apex II diffractometer using Mo Kα radiation(λ=0.71073 Å). The structures were solved by direct methods using theprogram SHELXS and refined by SHELXL. Hydrogen atoms connected to carbonwere placed at idealized positions using standard riding models andrefined isotropically. All non-hydrogen atoms were refinedanisoptriocally.

Crystals of 4b were grown by vapor diffusion of Et₂O into a solution ofthe complex in DCM. The structure was refined successfully without anydisorder and no solvent molecules were found in the crystal lattice.FIG. 8 shows the X-ray structure of complex 4b (ORTEP view, displacementellipsoids drawn at 50% probability level.) Hydrogen atoms were omittedfor clarity.

Crystals of 4b-Na were grown by vapor diffusion of Et₂O into a solutionof the complex in DCM. Each asymmetric unit contains two molecules ofthe palladium complexes and two BAr^(F) ₄− anions. The 2-methoxyphenylgroup (C44-C49) in Pd2 show positional disorder and was refined in twopossible orientations, with about 75.3% and 24.7% occupancies in themajor and minor components, respectively. Several of the CF₃-groups inthe borate anion show rotational disorder. For carbons C77, C86, C102,and C111, the three fluorine atoms attached to them were modeled using atwo-part disorder using similarity bond distance restraints. For carbonsC103 and C119, which display severe CF₃ disorder, a three-part disorderwas used to model the positions of their fluorine atoms (thethree-components were refined with a total occupancy of 1.0±0.001standard deviation). FIG. 9 shows the X-ray structure of complex 4b-Na(ORTEP view, displacement ellipsoids drawn at 50% probability level.)Hydrogen atoms and BAr^(F) ₄− anion were omitted for clarity.

Crystals of 5b were grown by vapor diffusion of Et₂O into a solution ofthe complex in DCM. The asymmetric unit contains a single molecule ofthe palladium complex and a hexafluoroantimonate anion. The structuresdo not show any disorder and solvent molecules were not found. FIG. 10shows the X-ray structure of complex 5b (ORTEP view, displacementellipsoids drawn at 50% probability level.) Hydrogen atoms andhexafluoroantimonate anion were omitted for clarity.

EXAMPLE 6. NICKEL-ALKALI CATALYSTS

Commercial reagents were used as received. All air- and water-sensitivemanipulations were performed using standard Schlenk techniques or undera nitrogen atmosphere using a drybox. Anhydrous solvents were obtainedfrom an Innovative Technology solvent drying system saturated withargon. High-purity polymer grade ethylene was obtained from MathesonTriGas without further purification. The NaBAr^(F) ₄ salt was preparedaccording to a literature procedure.

NMR spectra were acquired using JEOL spectrometers (ECA-400, −500, and−600) and referenced using residual solvent peaks. All ¹³C NMR spectrawere proton decoupled. ³¹P NMR spectra were referenced to phosphoricacid. ¹H NMR spectroscopic characterization of polymers: each NMR samplecontained ˜20 mg of polymer in 0.5 mL of 1,1,2,2-tetrachloroethane-d₂(TCE-d₂) and was recorded on a 500 MHz spectrometer using standardacquisition parameters at 120° C. High-resolution mass spectra wereobtained from the mass spectral facility at the University of Houston.Elemental analyses were performed by Atlantic Microlab. Gel permeationchromatography (GPC) data were obtained using a Malvern high temperatureGPC instrument equipped with refractive index, viscometer, and lightscattering detectors at 150° C. with 1,2,4-trichlorobenzene (stabilizedwith 125 ppm BHT) as the mobile phase. A calibration curve wasestablished using polystyrene standards in triple detection mode. Allmolecular weights reported are based on the triple detection method.

FIG. 11 shows Scheme 2 for the synthesis of nickel phenoxyphosphinecomplexes. Step a: 1) NaH, THF, 2) NiPhBr(PMe₃)₂; Step b: NaBAr^(F) ₄.PEG3=CH₂(OCH₂CH₂)₃OCH₃. The PEGylated ligand 13 was synthesized using amulti-step procedure outlined below. Metallation of 13 was achieved bydeprotonation using sodium hydride, followed by the addition ofNiPhBr(PMe₃)₂ to provide complex Ni11. As a standard catalyst, theconventional nickel phenoxyphosphine complex featuring ortho tert-butylgroups (Ni10) was also prepared. FIG. 12 shows steps in the synthesis ofcomplex Ni10. FIG. 13 shows steps in the synthesis of complex Ni11. FIG.14 shows steps in the synthesis of compound 11. More details areprovided below.

Preparation of (P(2-MeOPh)₂Cl:

A 200 mL Schlenk flask was charged with magnesium turnings (1.2 g, 50mmol, 2.5 equiv.) under nitrogen in 50 mL of dry THF. The compound2-bromoanisole (5.2 mL, 40 mmol, 2.0 equiv.) was added to the reactionmixture and then stirred at RT for 3 h until the solution turned darkgray. The resulting Grignard reagent was slowly cannula transferred overa period of 45 min to a solution of PCl₃ (1.6 mL, 20 mmol, 1.0 equiv.)in 100 mL of dry THF at −78° C. After the addition was complete, theheterogeneous mixture was continued stirring and allowed to warm up toRT overnight. Finally, the solvent was removed under vacuum and thecrude product was used in the next step without further purification.³¹P NMR (CDCl₃, 162 MHz): δ (ppm)=69.94 (s), 62.56 (s).

Preparation of Compound 2:

The compound 2-tert-butyl-4-cresol (6.73 g, 40.95 mmol, 1.05 equiv.) wasdissolved in 100 mL of dry DCM in a 200 mL Schlenk flask. The flask wascovered with aluminum foil and cooled to 0° C. Bromine (2 mL, 39 mmol,1.00 equiv.) was added dropwise to the reaction flask and the mixturewas allowed to warm to RT and stirred overnight. The reaction wasquenched by the slow addition of cold H₂O (75 mL) and was then extractedinto DCM (2×150 mL). The organic layers were combined, washed withaqueous NaHCO₃ (2×100 mL), H₂O (2×100 mL), dried over Na₂SO₄, filtered,and evaporated to dryness. The crude material was purified by silica gelcolumn chromatography (20:1 hexane:ethyl acetate) to afford a whitesolid (9.50 g, 39.07 mmol, 95%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=7.16(s, 1H), 7.01 (s, 1H), 5.64 (s, 1H), 2.26 (s, 3H), 1.40 (s, 9H). ¹³C NMR(CDCl₃, 101 MHz): δ (ppm)=148.21, 137.24, 130.30, 129.69, 127.46,111.97, 35.36, 29.47, 20.68.

Preparation of Compound 3:

To a mixture of 2 (9.50 g, 39.07 mmol, 1.0 equiv.) in 100 mL of dry THFin a 200 mL Schlenk flask under nitrogen at −0° C., small aliquots ofNaH (60%, 2.34 g, 58.6 mmol, 1.5 equiv.) were added and the mixture wasstirred at RT for 2 h. The reagent 2-methoxyethoxymethyl chloride(MEMCl) (5.5 mL, 44.93 mmol, 1.15 equiv.) was added and the solution wasstirred overnight. The reaction was quenched by the slow addition of H₂Oand the product was extracted into Et₂O (2×150 mL). The organic layerswere combined, washed with H₂O (2×75 mL), dried over Na₂SO₄, filtered,and evaporated to dryness. The crude material was purified by silica gelcolumn chromatography (20:1 hexane:ethyl acetate) to afford a colorlessoil (6.91 g, 20.86 mmol, 53%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=7.22 (d,J_(HH)=1.8 Hz, 1H), 7.07 (d, J_(HH)=1.8 Hz, 1H), 5.27 (s, 2H), 4.05 (m,2H), 3.65 (m, 2H), 3.41 (s, 3H), 2.26 (s, 3H), 1.40 (s, 9H). ¹³C NMR(CDCl₃, 101 MHz): δ (ppm)=150.46, 145.06, 134.56, 132.14, 127.69,117.74, 98.21, 71.72, 69.45, 59.18, 35.65, 30.94, 20.83. HRMS-ESI(+):Calc. for C₁₅H₂₃BrO₃[M+Na]⁺=353.0728, Found=353.0853.

Preparation of Compound 4:

To a solution of compound 3 (6.62 g, 20 mmol, 1.0 equiv.) in 50 mL ofdry THF in a 100 mL Schlenk flask under nitrogen at −78° C., nBuLi (1.6M in hexanes, 12.8 mL, 20.5 mmol, 1.02 equiv.) was added dropwise usinga syringe pump. The reaction mixture was stirred at −78° C. for 40 min Asolution of P(2-MeOPh)₂Cl (5.05 g, 18 mmol, 0.9 equiv.) in 50 mL of dryTHF was cannula transferred into the reaction mixture and stirred foranother 40 min. The reaction was quenched by the slow addition of H₂Oand the product was extracted into Et₂O (3×75 mL). The organic layerswere combined, washed with H₂O (2×50 mL), dried over Na₂SO₄, filtered,and evaporated to dryness. The crude material was purified by silica gelcolumn chromatography (4:1 hexane:ethyl acetate) to afford a colorlessoil (4.02 g, 8.09 mmol, 40%). This compound was used directly in thenext step without further purification.

Preparation of Compound 5:

Compound 4 (1.24 g, 2.5 mmol, 1.0 equiv.) was dissolved in 100 mL ofMeOH and then 10 mL solution of 2 M HCl in Et₂O was added. The reactionmixture was stirred at RT overnight and then dried to remove solvent.The product was dissolved in 200 mL of EtOAc along and then combinedwith 50 mL of 1 M aqueous NaHCO₃. The mixture was stirred at RT for 30min and the product was extracted into Et₂O (2×100 mL). The organiclayers were combined, washed with H₂O (2×100 mL), dried over Na₂SO₄,filtered, and evaporated to dryness. The crude material was purified bysilica gel column chromatography (4:5 hexane:ethyl acetate) to afford awhite solid (0.69 g, 1.68 mmol, 67%). ¹H NMR (CDCl₃, 500 MHz): δ(ppm)=7.40 (d, J_(HH)=11.5 Hz, 1H), 7.19 (ddd, J_(HH)=7.4, 5.6, 1.7 Hz,2H), 7.13 (d, J_(HH)=1.8 Hz, 1H), 7.02 (td, J_(HH)=8.1, 1.5 Hz, 2H),6.97 (dd, J_(HH)=5.4, 1.6 Hz, 1H), 6.70 (t, J_(HH)=7.5 Hz, 2H), 6.37(dd, J_(HH)=8.1, 5.1 Hz, 2H), 3.07 (s, 6H), 1.92 (s, 3H), 1.51 (s, 9H).¹³C NMR (CDCl₃, 100 MHz): δ (ppm)=161.04 (d, J_(CP)=15.1 Hz), 156.56 (d,J_(CP)=19.7 Hz), 135.36, 133.23, 133.0.3 (d, J_(CP)=3.2 Hz), 130.24,129.53, 128.42, 123.09 (d, J_(CP)=2.8 Hz), 120.96, 119.28, 110.30,55.71, 34.79, 29.54, 20.88. ³¹P NMR (CDCl₃, 162 MHz): δ (ppm)=−51.71.HRMS-ESI(+): Calc. for C₂₅H₂₉O₃P [M+Na]⁺=431.1752, Found=431.1887.

Preparation of Compound 7:

Solid 2,6-dibromo-4-methylphenol (6.65 g, 25 mmol, 1.0 equiv.) wasdissolved in 100 mL of dry THF in a Schlenk flask under nitrogen andcooled to 0° C. Small aliquots of NaH (60%, 1.48 g, 37 mmol, 1.5 equiv.)were added and the mixture was stirred at room temperature for 1 h. Thereagent 2-methoxyethoxymethyl chloride (MEMCl) was added and theresulting solution was stirred overnight. The reaction was quenched bythe slow addition of H₂O and the products were extracted into Et₂O(2×100 mL). The organic layers were combined, washed with H₂O (2×50 mL),dried over Na₂SO₄, filtered, and evaporated to dryness. The crudematerial was purified by silica gel column chromatography (2:1hexane:ethyl acetate) to afford a clear oil (7.66 g, 21.64 mmol, 86%).¹H NMR (CDCl₃, 500 MHz): δ (ppm)=7.29 (s, 2H), 5.20 (s, 2H), 4.08 (m,2H), 3.61 (m, 2H), 3.38 (s, 3H), 2.24 (s, 3H). ¹³C NMR (CDCl₃, 126 MHz):δ (ppm)=149.04, 136.91, 133.35, 117.97, 98.36, 71.77, 69.89, 59.19,20.29. HRMS-ESI(+): Calc. for C₁₁H₁₄Br₂O₃[M+Na]⁺=374.9202,Found=374.9332.

Preparation of Compound 8:

To a solution of 7 (7.08 g, 20 mmol, 1.0 equiv.) in 50 mL of dry THF ina Schlenk flask under nitrogen at −78° C., nBuLi (1.6 M in hexanes, 12.8mL, 20.5 mmol, 1.02 equiv.) was added dropwise using a syringe pump. Thereaction mixture was then stirred at −78° C. for 40 min. A solution ofP(2-MeOPh)₂Cl (5.05 g, 18 mmol, 0.9 equiv.) in 50 mL of dry THF wascannula transferred to the reaction mixture and stirred for another 40min. The reaction was quenched by the slow addition of H₂O and theproducts were extracted into Et₂O (3×75 mL). The organic layers werecombined, washed with H₂O (2×50 mL), dried over Na₂SO₄, filtered, andevaporated to dryness. The crude material was purified by silica gelcolumn chromatography (3:1 hexane:ethyl acetate) to afford a colorlessoil (6.82 g, 13.16 mmol, 73%). ¹H NMR (CDCl₃, 500 MHz): δ (ppm)=7.36 (s,1H), 7.32 (t, J_(HH)=7.5 Hz, 2H), 6.86 (m, 3H), 6.83 (d, J_(HH)=5.2 Hz,1H), 6.63 (m, 2H), 6.49 (m, 1H), 5.30 (s, 2H), 4.02 (t, J_(HH)=4.8 Hz,2H), 3.72 (s, 6H), 3.52 (t, J_(HH)=4.5 Hz, 2H), 3.34 (s, 3H), 2.12 (s,3H). ¹³C NMR (CDCl₃, 126 MHz): δ (ppm)=161.33 (d, J_(CP)=16.5 Hz),161.20 (d, J_(CP)=20.9), 154.24, 154.07, 135.61, 134.78, 134.50, 133.86,132.94 (d, J_(CP)=17.4 Hz), 132.81, 130.34, 124.31, 124.20 (d,J_(CP)=13.7 Hz), 121.18, 117.34, 117.32, 110.22, 98.75 (d, J_(CP)=9.4Hz), 98.68, 71.81, 69.52 (d, J_(CP)=4.3 Hz), 59.07, 55.75, 20.66. ³¹PNMR (CDCl₃, 162 MHz): δ (ppm)=−35.90. HRMS-ESI(+): Calc. for C₂₅H₃₀BrO₅P[M+Na]⁺=541.0750, Found=541.0940.

Preparation of Compound 9:

To a solution of 8 (6 g, 11.58 mmol, 1.0 equiv.) in 50 mL of dry THF ina Schlenk flask under nitrogen at −78° C., nBuLi (1.6 M in hexanes, 8.4mL, 13.44 mmol, 1.16 equiv.) was added dropwise using a syringe pump.The reaction mixture was stirred at −78° C. for 40 min. Dry DMF (5 mL,65 mmol, 5.6 equiv.) was added to the reaction mixture and stirred foranother 40 min. The reaction was quenched by the slow addition of H₂Oand the product was extracted into Et₂O (3×75 mL). The organic layerswere combined, washed with H₂O (2×50 mL), dried over Na₂SO₄, filtered,and evaporated to dryness. The crude material was purified by silica gelcolumn chromatography (3:2 hexane:ethyl acetate) to afford a lightyellow oil (4.67 g, 9.98 mmol, 86%). This compound was used directly inthe next step without further purification.

Preparation of Compound 10:

Compound 9 (4.67 g, 9.98 mmol, 1.0 equiv.) was dissolved in 400 mL ofMeOH and 80 mL of THF. Small aliquots of NaBH₄ (2 g, 54 mmol, 5.4equiv.) were added and the mixture was stirred at RT overnight. Thereaction solvent was removed under vacuum and the residue wasredissolved in Et₂O (100 mL). The ether layer was washed with H₂O (2×100mL), dried over Na₂SO₄, filtered, and evaporated to dryness. The crudematerial was purified by silica gel column chromatography (1:3hexane:ethyl acetate) to afford a white solid (3.8 g, 8.08 mmol, 81%).¹H NMR (CDCl₃, 600 MHz): δ (ppm)=7.33 (t, J_(HH)=7.6 Hz, 2H), 7.20, (s,1H), 6.87 (dd, J_(HH)=8.4, 5.5 Hz, 2H), 6.84 (t, J_(HH)=7.4 Hz, 2H),6.62 (m, 2H), 6.51 (m, 1H), 5.29 (s, 2H), 4.62 (s, 2H), 3.88 (m, 2H),3.72 (s, 6H), 3.57 (m, 2H), 3.36 (s, 3H), 2.14 (s, 3H). ¹³C NMR (CDCl₃,126 MHz): δ (ppm)=161.21 (d, J_(CP)=16.6 Hz), 157.74 (d, J_(CP)=20.6Hz), 135.24, 134.73, 134.37, 133.78, 132.59, 130.25, 129.79 (d,J_(CP)=12.2 Hz), 124.29 (d, J_(CP)=12.3 Hz), 121.08, 110.15, 99.92 (d,J_(CP)=13.1 Hz), 71.50, 69.16, 61.02, 59.11, 55.74, 20.94. ³¹P NMR(CDCl₃, 162 MHz): δ (ppm)=−38.50. HRMS-ESI(+): Calc. forC₁₄H₂₀O₆[M+Na]⁺=493.1751, Found=493.1925.

Preparation of Compound 11:

Triethylene glycol monomethyl ether (2.63 g, 16 mmol, 1.0 equiv.) wasdissolved in 100 mL of dry THF in a Schlenk flask under nitrogen andcooled to 0° C. Small aliquots of NaH (60%, 1 g, 25 mmol, 1.56 equiv.)were added and the mixture was stirred at RT for 1 h. The reagent2,4,6-triisopropylbenzenesulfonyl chloride (6.1 g, 20 mmol, 1.25 equiv.)was added and the solution was stirred overnight. The reaction wasquenched by the slow addition of H₂O and the product was extracted intoEt₂O (2×100 mL). The organic layers were combined, washed with H₂O (3×50mL), dried over Na₂SO₄, filtered, and evaporated to dryness. The crudematerial was purified by silica gel column chromatography (5:1hexane:ethyl acetate to 1:3 hexane:ethyl acetate) to afford a colorlessoil (5.14 g, 11.95 mmol, 75%). ¹H NMR (CDCl₃, 500 MHz): δ (ppm)=7.16 (s,2H), 4.14 (m, 4H), 3.71 (t, J_(HH)=4.8 Hz, 2H), 3.59 (m, 6H), 3.50 (m,2H), 3.34 (s, 3H), 2.89 (sep, J_(HH)=6.9 Hz, 1H), 1.24 (m, 18H). ¹³C NMR(CDCl₃, 126 MHz): δ (ppm)=153.77, 150.93, 129.35, 123.84, 71.96, 70.78,70.64, 68.87, 68.22, 59.12, 34.34, 29.67, 24.80, 23.65. HRMS-ESI(+):Calc. for C₂₂H₃₈O₆S [M+Na]⁺=453.2287, Found=453.2442.

Preparation of Compound 12:

To a mixture of 11 (3.8 g, 8.08 mmol, 1 equiv.) in 100 mL of dry THF ina Schlenk flask under nitrogen at −0° C., small aliquots of NaH (60%,1.3 g, 32.4 mmol, 4 equiv.) was added. The reaction mixture stirred atRT for 1 h. A solution of compound 11 (5.23 g, 12.15 mmol, 1.5 equiv.)in 50 mL of THF was cannula transferred into the reaction mixture andthen stirred at RT overnight. The reaction was quenched by the slowaddition of cold H₂O and the product was extracted into Et₂O (3×100 mL).The organic layers were combined, washed with H₂O (2×75 mL), dried overNa₂SO₄, filtered, and evaporated to dryness. The crude material waspurified by silica gel column chromatography (1:1 hexane: ethyl acetateto 1:4 hexane:ethyl acetate) to afford a colorless oil (3.95 g, 6.07mmol, 75%). This compound was used directly in the next step withoutfurther purification.

Preparation of Compound 13:

Compound 12 (3.95 g, 6.07 mmol, 1 equiv.) was dissolved in 100 mL ofMeOH and then treated with 10 mL of 2 M HCl in Et₂O. The reactionmixture was stirred at RT overnight. The solvent was removed undervacuum and the product was dissolved in 200 mL of EtOAc. A 50 mLsolution of 1 M NaHCO₃ in H₂O was then added. The mixture was stirred atRT for 30 min and the product was extracted into Et₂O (2×100 mL). Theorganic layers were combined, washed with H₂O (2×100 mL), dried overNa₂SO₄, filtered, and evaporated to dryness. The crude material waspurified by silica gel column chromatography (1:3 hexane:ethyl acetate)to afford a white waxy solid (2.9 g, 5.49 mmol, 90%). ¹H NMR (CDCl₃, 500MHz): δ (ppm)=7.32 (td, J_(HH)=7.7, 1.5 Hz, 2H), 7.23 (d, J_(HH)=1 Hz,1H), 6.97 (d, J_(HH)=1.7 Hz, 1H), 6.85 (m, 4H), 6.77 (m, 2H), 6.52 (m,J_(HH)=5.1, 1.9 Hz, 1H), 4.66 (s, 2H), 3.73 (s, 6H), 3.68 (m, 2H), 3.66(m, 2H), 3.60 (m, 2H), 3.58 (m, 4H), 3.49 (m, 2H), 3.35 (s, 3H), 2.11(s, 3H). ¹³C NMR (CDCl₃, 126 MHz): δ (ppm)=161.53 (d, J_(CP)=26.8 Hz),161.40 (d, J_(CP)=5.5 Hz), 155.96 (d, J_(CP)=29.7 Hz), 155.87, 134.34,133.74 (d, J_(CP)=6.6 Hz), 130.62, 130.22, 129.04 (d, J_(CP)=9.6 Hz),123.91, 122.57 (d, J_(CP)=6.1 Hz), 121.04, 110.32, 71.98, 70.99, 70.76,70.61, 70.40, 69.73, 59.11, 55.81, 20.71. ³¹P NMR (CDCl₃, 162 MHz): δ(ppm)=−44.09. HRMS-ESI(+): Calc. for C₂₉H₃₉O₇P [M+Na]⁺=551.2175,Found=551.2362.

Preparation of Complex NiPhBr(PMe)₂:

Inside the glovebox, Ni[COD]₂ (1.10 g, 4 mmol, 1 equiv.) and PMe₃ (1 Min THF, 10 mL, 10 mmol, 2.5 equiv.) were dissolved in 50 mL of dry Et₂O.PhBr (0.94 g, 6.0 mmol, 1.5 equiv.) was added and the reaction mixturewas stirred at RT for 6 h. The solution was filtered to remove a blacksolid and the filtrate was then dried completely under vacuum. The crudematerial was washed with cold Et₂O (−30° C., 4×4 mL) to afford a brightorange solid (1.02 g, 3.17 mmol, 79%). ¹H NMR (C₆D₆, 500 MHz): δ(ppm)=7.28 (dd, J_(HH)=7.7, 1.1 Hz, 2H), 6.91 (t, J_(HH)=7.5 Hz, 2H),6.75 (m, 1H), 0.78 (t, J_(HH)=3.9 Hz, 18H). ³¹P NMR (C₆D₆, 202 MHz): δ(ppm)=−14.78.

Preparation of Complex Ni10:

Inside the glovebox, ligand 15 (0.164 g, 0.4 mmol, 1.0 equiv.) wasdissolved in 10 mL of THF. Small aliquots of NaH (60%, 0.32 g, 0.8 mmol,2.0 equiv.) were added and the mixture was stirred at RT for 2 h. Thesolution was filtered to remove excess NaH and then combined with asolution of NiPhBr(PMe₃)₂ (0.122 g, 0.38 mmol, 0.95 equiv.) in 5 mL ofbenzene. The resulting mixture was stirred at RT overnight. Theprecipitate formed was removed by filtration and the filtrate was driedunder vacuum. The crude material was dissolved in a mixture of 15 mL ofpentane and 2 mL of toluene and the solution was filtered once againbefore evaporating to dryness. Finally, the resulting solid was washedwith pentane (3×2 mL) and dried under vacuum to afford a yellow powder(0.11 g, 0.17 mmol, 45%). ¹H NMR (C₆D₆, 500 MHz): δ (ppm)=7.56 (ddd,J_(HH)=11.1, 7.5, 1.3 Hz, 2H), 7.23 (d, J_(HH)=7.5 Hz, 2H), 7.14 (d,J_(HH)=2.0 Hz, 1H), 7.04-6.98 (m, 2H), 6.97-6.92 (m, 1H), 6.71 (t,J_(HH)=7.4 Hz, 2H), 6.63 (t, J_(HH)=7.5 Hz, 2H), 6.58 (d, J_(HH)=7.3 Hz,1H), 6.38 (dd, J_(HH)=8.1, 4.4 Hz, 2H), 2.98 (s, 6H), 2.04 (s, 3H), 1.69(s, 9H), 0.81 (d, J_(HH)=8.8 Hz, 9H). ¹³C NMR (C₆D₆, 152 MHz): δ(ppm)=174.11 (d, J_(CP)=26.3 Hz), 160.74 (d, J_(CP)=5.5 Hz), 150.92 (d,J_(CP)=32.6 Hz), 137.70 (d, J_(CP)=9 Hz), 137.09 (d, J_(CP)=2.8 Hz),133.99 (d, J_(CP)=5.4 Hz), 130.85, 130.72, 130.47, 125.22, 121.86 (d,J_(CP)=6.8 Hz), 120.47 (d, J_(CP)=8.3 Hz), 120.29, 119.86, 118.69,118.20, 110.66 (d, J_(CP)=4.4 Hz), 54.88, 35.13, 29.54, 20.60, 12.47 (d,J_(CP)=23.8 Hz). ³¹P NMR (C₆D₆, 202 MHz): δ (ppm)=15.08 (d, J_(PP)=320.9Hz), −13.64 (d, J_(PP)=320.7 Hz). Anal. Calcd for C₃₄H₄₂NiO₃P₂: C,65.94; H, 6.84. Found: 65.68; 6.99.

Preparation of Complex Ni11:

Inside the glovebox, ligand 13 (1.12 g, 2.11 mmol, 1.0 equiv.) wasdissolved in 50 mL of dry THF. Small aliquots of NaH (60%, 0.17 g, 4.22mmol, 2.0 equiv.) were added and the mixture was stirred at RT for 2 h.The mixture was filtered to remove excess NaH and then a solution ofNiPhBr(PMe₃)₂ (0.65 g, 2.02 mmol, 0.96 equiv.) in 20 mL of benzene wasadded. The resulting mixture was stirred at RT overnight. The next day,the solution was filtered to remove the precipitate and the filtrate wasdried completely under vacuum. The crude material was dissolved in amixture of 40 mL of pentane and 4 mL of benzene. Another filtration wasperformed to remove the precipitate and the filtrate was dried onceagain. Finally, the resulting solid was washed with pentane (3×5 mL) anddried to under vacuum to afford a yellow powder (1.12 g, 1.51 mmol,75%). ¹H NMR (C₆D₆, 500 MHz): δ (ppm)=7.64 (m, 2H), 7.37 (d, J_(HH)=1.7Hz, 1H), 7.24 (d, J_(HH)=7.7 Hz, 2H), 7.06 (dd, J_(HH)=8.0, 4.4 Hz, 1H),7.02 (m, 2H), 6.74 (t, J_(HH)=7.4 Hz, 2H), 6.66 (t, J_(HH)=7.5 Hz, 2H),6.61 (m, 1H), 4.87 (s, 2H), 3.74 (m, 2H), 3.60 (m, 2H), 3.50 (m, 2H),3.44 (m, 4H), 3.30 (m, 2H), 3.07 (s, 3H), 2.95 (s, 6H), 2.03 (s, 3H),0.81 (d, 9H). ¹³C NMR (C₆D₆, 152 MHz): δ (ppm)=173.39 (d, J_(CP)=26.8Hz), 160.77 (d, J_(CP)=4.8 Hz), 150.91 (d, J_(CP)=29.7 Hz), 137.05,133.93 (d, J_(CP)=6.3 Hz), 132.86, 131.74, 131.00, 127.16 (d, J_(CP)=9.5Hz), 125.22, 120.46, 120.39, 120.31, 120.07, 119.71, 117.92, 117.54,110.52 (d, J_(CP)=3.8 Hz), 72.09, 70.99, 70.85, 70.80, 70.63, 69.89,69.82, 58.42, 54.81, 20.45, 11.50 (d, J_(CP)=24.7 Hz). ³¹P NMR (C₆D₆,202 MHz): δ (ppm)=13.74 (J_(PP)=319.5 Hz), −12.74 (J_(PP)=318.1 Hz).Anal. Calcd for C₃₈H₅₂NiO₇P₂: C, 61.72; H, 6.82. Found: 61.63; 6.96.

EXAMPLE 7. METAL-BINDING STUDIES

UV-Vis Absorption Spectroscopy: Metal Titration. To determine whetherNa⁺ can coordinate to Ni11, metal titration studies were carried out byUV-visible absorption spectroscopy. Stock solutions of Ni11 andNaBAr^(F) ₄ were prepared inside an inert nitrogen-filled glovebox. A500 μM stock solution of Ni11 were obtained by dissolving 25 μmol ofNi11 in 50 mL of Et₂O. A 10 mL aliquot of this 500 μM solution wasdiluted to 50 mL using a volumetric flask to give a final concentrationof 100 μM. The 3.0 mM stock solution of NaBAr^(F) ₄ was obtained bydissolving 30 μmol of NaBAr^(F) ₄ in 10 mL of Et₂O using a volumetricflask. A 3.0 mL solution of Ni11 was transferred to a 1 cm quartzcuvette and then sealed with a septum screw cap. A 100 μL airtightsyringe was loaded with the 3.0 mM solution of NaBAr^(F) ₄. The cuvettewas placed inside a UV-vis spectrophotometer and the spectrum of theNi11 solution was recorded. Aliquots containing 0.1 equiv. of NaBAr^(F)₄ (10 μL), relative to the nickel complex, were added and the solutionwas allowed to reach equilibrium before the spectra were measured (about20-30 min). The titration experiments were stopped after the addition ofup to 1.0 equiv. of NaBAr^(F) ₄.

FIG. 15 shows UV-vis absorbance spectra of complex Ni11 (100 μM in Et₂O)after the addition of various aliquots of NaBAr^(F) ₄. The startingtrace of Ni11 is shown with the final trace (+1.0 equiv. of Na⁺ relativeto Ni). When aliquots of NaBAr^(F) ₄ (where BAr^(F)₄−=tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) were added to asolution of Ni11 in Et₂O, the optical band at ˜370 nm graduallydecreased while the optical band at ˜330 nm increased. The appearance ofisosbestic points at 326 and 359 nm suggests that the addition of Na⁺ toNi11 led to the formation of a new optically active species.

UV-Vis Absorption Spectroscopy: Job Plot Studies. Stock solutions ofNi11 (500 μM) and NaBAr^(F) ₄ (500 μM) in Et₂O were prepared in separatevolumetric flasks inside the drybox. Stock solutions of Ni11 andNaBAr^(F) ₄ were combined in different ratios to give 10 differentsamples, each having a final volume of 3.0 mL. The samples were recordedby UV-vis absorption spectroscopy at RT. The UV-vis spectral data wereanalyzed according to a method previously reported. In this case, thehost (H) was Ni11, the guest (g) was Na⁺, and the complex (C) wasNi11-Na. Since the sodium salt has no absorption in the 300-500 nmrange, this simplified expression was used to analyze the data:A_(obs)−ε_(h)·[H]_(t)=(ε_(C)−a·ε_(h))·[C], where A_(obs)=observedabsorbance, a=constant, ε_(h)=molar absorptivity of host Ni11,ε_(C)=molar absorptivity of Ni11-Na, [H]_(t)=starting concentration ofhost Ni11, and [C]=observed concentration of Ni11-Na. Since [C] isproportional to A_(obs)-ε_(h)·[H]_(t), a Job Plot was constructed byplotting A_(obs)−ε_(h)·[H]_(t) vs. χ_(Ni) (the mole ratio ofNi11=[Ni11]/([Ni11]+[Na⁺])). Table 9 below shows the data andcalculations used for the Job Plot.

TABLE 9 Data and Calculations Used for Job Plot Volume of Amount FinalStock Soln of H Conc. A_(h) A_(obs) of H Added of H (cal- (@330 χ^(Ni)(mL) (mol) (M) culated) nm) A_(obs) − A_(h) 1.0 3.000E−03 1.500E−065.000E−04 2.663E+00 2.663E+ −2.040E− 00 04 0.9 2.700E−03 1.350E−064.500E−04 2.396E+00 2.350E+   4.576E− 00 02 0.8 2.400E−03 1.200E−064.000E−04 2.130E+00 1.966E+   1.637E− 00 01 0.7 2.100E−03 1.050E−063.500E−04 1.864E+00 1.653E+   2.108E− 00 01 0.6 1.800E−03 9.000E−073.000E−04 1.598E+00 1.308E+   2.896E− 00 01 0.5 1.500E−03 7.500E−072.500E−04 1.331E+00 1.008E+   3.234E− 00 01 0.4 1.200E−03 6.000E−072.000E−04 1.065E+00 8.275E−   2.375E− 01 01 0.3 9.000E−04 4.500E−071.500E−04 7.988E−01 6.497E−   1.491E− 01 01 0.2 6.000E−04 3.000E−071.000E−04 5.325E−01 4.393E−   9.315E− 01 02 0.1 3.000E−04 1.500E−075.000E−05 2.663E−01 2.714E− −5.174E− 01 03In Table 9, the molar absorptivity of H (ε_(h)) at 330 nm=5325 M⁻¹cm⁻¹.Stock solution of H was 500 μM.

FIG. 16 is a Job Plot showing the coordination interactions betweencomplex Ni11 and NaBAr^(F) ₄. The peak maximum occurs at χ_(Ni)=0.5,which suggests that the optimal nickel:sodium binding stoichiometry is1:1. The y-axis value (A_(obs)−ε_(h)·[H]_(t)) is proportional to theconcentration of the nickel-sodium complex Ni11-Na. The x-axis is themolar ratio of nickel (χ_(Ni)=[Ni11]/([Ni11]+[Na⁺])).

EXAMPLE 8. STRUCTURAL CHARACTERIZATION

To obtain structural characterization, single crystals of thenickel-sodium complex were grown by layering pentane over a toluene/Et₂Osolution of Ni11 and NaBAr^(F) ₄ (1:1). Single crystals suitable forX-ray diffraction studies were picked out of the crystallization vialsand mounted onto Mitogen loops using Paratone oil. The crystals werecollected at a 6.0 cm detector distance at −150° C. on a Brucker Apex IIdiffractometer using Mo Kα radiation (λ=0.71073 Å). The structures weresolved by direct methods using the program SHELXT and refined bySHELXLE. Hydrogen atoms connected to carbon were placed at idealizedpositions using standard riding models and refined isotropically. Allnon-hydrogen atoms were refined anisoptriocally. FIG. 17A shows theX-ray structure of complex Ni11-Na (ORTEP view, displacement ellipsoidsdrawn at 50% probability level). Hydrogen atoms and the BAr^(F) ₄− anionwere omitted for clarity. Its X-ray structure revealed aheterobimetallic complex with the compositionNiNa(phenoxyphosphine-PEG)Ph(PMe₃). The nickel centre isfour-coordinate, in which the phenyl group is coordinated trans relativeto the phosphorus donor P(1). Presumably, this orientation is preferreddue to metal-π interactions between the adjacent sodium ion and phenylring (C(30)-C(31)). The sodium is ligated by four PEG oxygen atoms and aphenolate donor. Although complex Ni11 itself could not be crystallizedfor X-ray diffraction analysis, the structure of the related mononickelNi10 in FIG. 17B shows that the nickel centre is square planar but thecoordinated phenyl group is cis relative to P(1). Crystals of complexNi10 were grown by layering of pentane into a solution of the complex intoluene at −30° C. The three methyl carbons (C32-C34) attached to thephosphine atom were refined in two parts due to positional disorder. Thesolvent molecule pentane was refined successfully without the use of anystructural restraints. Interestingly, when a solution of Ni10 in Et₂Owas treated with up to 4 equiv. of NaBAr^(F) ₄, no UV-visible absorptionchanges were observed, indicating that there are no coordinationinteractions between complex Ni10 and Na⁺.

EXAMPLE 9. POLYMERIZATION STUDIES

General Procedure for Ethylene Polymerization. Inside the drybox, thenickel complex Ni11 (0.5 μmol) and NaBAr^(F) ₄ (1 μmol) were dissolvedin 10 mL of toluene in a 20 mL vial and stirred for 10 min SolidNi(COD)₂ (4 μmol) was added and stirred until a clear solution wasobtained (4-5 min). The mixture was loaded into a 10 mL syringe equippedwith an 8-inch stainless steel needle. The loaded syringe was sealed bysticking the needle tip into a rubber septum and brought outside of thedrybox. To prepare the polymerization reactor, 90 mL of dry toluene wasplaced in an empty autoclave. The autoclave was pressurized withethylene to 80 psi, stirred for 5 min, and then the reactor pressure wasreduced to 5 psi. This process was repeated 3 times to remove traceamounts of oxygen inside the reaction vessel. The reactor was thenheated to the desired temperature and the catalyst solution was injectedinto the autoclave through a side arm. The autoclave was sealed andpurged with ethylene at 40 psi (no stirring) three times. Finally, thereactor pressure was increased to the desired pressure, and the contentswere stirred vigorously. To stop the polymerization, the autoclave wasvented and cooled in an ice bath. A solution of MeOH (600 mL) was addedto precipitate the polymer. The polymer was collected by vacuumfiltration, rinsed with MeOH, and dried under vacuum at 80° C.overnight. The reported yields are average values obtained fromduplicate or triplicate runs.

To obtain consistent polymer yields from run to run, the amount ofcatalyst used in each run must be kept as consistent as possible. Since0.5 μmol of the Ni11 catalyst weighs only 0.37 mg, it is extremelydifficult to weigh out exactly this amount using a standard analyticalbalance. To minimize errors due to weighing inconsistencies, a batchcatalyst preparation method was used. First, 37 mg (50 μmol) of thecatalyst was weighed out and then dissolved into 50 mL of toluene. Thissolution was divided equally into 10 vials so that each vial contained 5μmol of catalyst. Next, each 5 μmol of catalyst was combined with 20 mLof toluene and this 25 mL mixture was partitioned into 10 vials so thateach vial contained 0.5 μmol of catalyst. Finally, each vial was driedcompletely under vacuum and stored in a refrigerator inside the dryboxuntil ready for use.

For all polymerization reactions, except ones that were performed todetermine the temperature profiles, the reaction temperature wascontrolled by manual cooling of the reactor with an air stream when thereactor increases more than 5° C. above the starting temperature. Toclean the Parr reactor, the vessel was washed with hot toluene (80° C.)to remove the polymer sample from the previous run and rinsed withacetone before drying under vacuum for at least 1 h to remove traceamounts of water.

Table 10 below shows the results of the polymerization studies. Tominimize catalyst thermal decomposition, the polymerization studies inTable 10 were performed using a low catalyst concentration of 5 μM andwith manual external cooling when necessary. Under these conditions,complex Ni10 produced linear polyethylene (PE) with an activity of2.12×10³ kg/mol·h (Table 10, entry 1). The addition of NaBAr^(F) ₄ toNi10 had negligible effects on polymerization (activity=1.88×10³kg/mol·h, entry 2), which further supports the observation that Na⁺ doesnot bind to Ni10.

TABLE 10 Ethylene Polymerization Data Initial Activity Pressure TimeTemp. (kg/ Entry Complex (psi) (h) (° C.) mol · h) 1 Ni10 450 1 30 21202 Ni10/Na⁺ 450 1 30 1880 3 Ni11 450 1 30 0 4 Ni11—Na 150 1 RT 3780 5Ni11—Na 300 1 RT 8840 6 Ni11—Na 450 1 RT 10800 7 Ni11—Na 450 0.5 3025300 8 Ni11—Na 450 1 30 18100 9 Ni11—Na 450 2 30 15080 10 Ni11—Na 450 1RT 10800 11 Ni11—Na 450 1 40 14700 12 Ni11—Na 450 1 50 13000 13 Ni11—Na450 1 60 9380For Table 10, conditions were: Ni catalyst (0.5 μmol), NaBAr^(F) ₄ (1μmol, if any), Ni(COD)₂ (4 μmol), 100 mL toluene. Temperature wascontrolled by manual external cooling when necessary to ensure that thereaction temperature does not exceed greater than 5° C. from thestarting temperature.

Surprisingly, when Ni11 was tested under the same conditions as above,no polyethylene was obtained (Table 10, entry 3). It was hypothesizedthat the free PEG chain in Ni11 can self-inhibit by occupying opencoordination sites at the nickel centre. However, when NaBAr^(F) ₄ wasadded to Ni11, the resulting nickel-sodium Ni11-Na showed a remarkablyactivity of 1.81×10⁴ kg/mol·h (entry 8), which is a ˜8.5×increase incomparison to that of Ni10. A comparison with several different nickelsystems reported in the literature indicates that Ni11-Na is among oneof the most active catalysts, only slower than nickel diimine and nickeltris(adamantyl)phosphine complexes, although different studies useddifferent polymerization conditions. The PE produced by Ni11-Na has lowmolecular weight (M_(n)=˜1.6×10³) and narrow polydispersity(M_(w)/M_(n)=˜1.4), which is typical for this class of catalysts.

To probe the polymerization behaviour of Ni11-Na further, its reactivitywas evaluated as a function of pressure, time, and temperature. When theethylene pressure was increased from 150→300→450 psi (Table 10, entries4-6), the catalyst activity also increased. The approximately linearcorrelation between pressure and polymerization rate suggests that thereaction is first-order in ethylene. At 150 psi and RT (Table S4),Ni11-Na showed relatively constant activity (average=3.3×10³ kg/mol·h)up to 3.0 h. However, at 450 psi and 30° C. (Table 10), the activitygradually decreased from 2.5×10⁴ (entry 7) to 1.5×10⁴ kg/mol·h (entry 9)over the course of 2 h, which is most likely indicative of catalystdecomposition. Finally, when polymerizations were performed at differenttemperatures (RT to 60° C., entries 8 and 10-13), the optimaltemperature was at 30° C. However, during the course of some reactions,there was a rapid spike in temperature that was difficult to control.This large exotherm only occurred when the Ni11-Na complex was used. Incontrast, polymerizations using the monometallic Ni10 and Ni11 complexesdid not generate any appreciable heat.

To gain further insights into the thermal stability of the Ni11-Nacomplex, reaction temperature and polymer yields were measured as afunction of time. FIG. 18A is a plot showing the reaction temperatures(dots) and polymer yields (triangles) during the course of a 60 min runby the Ni11-Na complex at 100 μM catalyst concentration and FIG. 18B isa plot of the same study using a 50 μM catalyst concentration. When a100 μM toluene solution of the nickel-sodium catalyst was treated withNi(COD)₂ and then exposed to 450 psi of ethylene, the reactiontemperature rose from RT (˜18-19° C.) to 159° C. in 4 min. After thisearly temperature burst, the solution cooled slowly back down to RTafter 60 min. Interestingly, when the products yields were determined at4 and 60 min, similar amounts of polymer were obtained (˜10.4 and ˜11.3g, respectively). This result suggests that the Ni11-Na catalyst wasdeactivated shortly after ˜4 min. When the Ni11-Na concentration waslowered to 50 μM, the maximum reaction temperature was observed at 122°C. after 5 min. The rate of polymer formation remained relativelyconstant from 0-7 min but then dropped precipitously thereafter. Onceagain, these data suggest that when the reaction temperature exceeded acertain maximum threshold, the Ni11-Na complex was no longer active.

This work illustrates the importance of conducting detailed temperaturestudies to accurately evaluate catalyst thermal stability. For example,reporting that the Ni11-Na catalyst was only active for 4 min at RT(FIG. 18A) would be somewhat misleading, since in actuality, thereaction temperature went up as high as 159° C. if no external coolingwas applied. The results of the detailed temperature studies are notnecessarily unique to the Ni11-Na system, since other highly activenickel catalysts have also been shown to exhibit large exotherms duringpolymerization. However, many literature reports only indicate thereactor temperature at the start of the reaction rather than thetemperature changes (and corresponding yields) during the polymerizationprocess. Oftentimes, the reaction temperature was either not regulatedor attempts to do so was not reported. This information is criticalbecause it enables the determination of the appropriate catalystconcentration needed to minimize uncontrollable exotherms and to operatewithin a temperature regime that leads to greatest catalystproductivity.

EXAMPLE 10. NICKEL-ALKALI PHOSPHINE PHOSPHONATE POLYETHYLENE GLYCOL(PEG) COMPLEXES

These examples relate to the incorporation of secondary metal ions toPd(II) phosphine-phosphonate complexes and demonstrate that theirpresence leads to enhanced catalytic performance A new series ofheterobimetallic nickel-metal complexes bearing phosphine-phosphonateester donors with polyethylene glycol (PEG) chains was synthesized.Based on metal binding studies, nickel phosphine phosphonatepolyethylene glycol (PEG) complexes can form 1:1 adducts with alkalications in solution. These nickel-alkali complexes are more active forethylene homopolymerization in comparison to parent mononickelcomplexes. In previous work, alkali BAr^(F) ₄ salts were used as thesecondary metal source because of their good solubility in hydrocarbonor halogenated solvents, which are standard solvent for polymerization.These examples demonstrate that nickel catalysts are active in the polarorganic solvent THF, which allowed for polymerization in the presence ofa wide variety of secondary metal salts. Alkaline metals (Ca²⁺, Mg²⁺)and transition metals (Co²⁺, Zn²⁺) ions can also coordinate to thecatalysts and facilitate ethylene and copolymerization.

Commercial reagents were used as received. All air- and water-sensitivemanipulations were performed using standard Schlenk techniques or undera nitrogen atmosphere using a glovebox. Anhydrous solvents were obtainedfrom an Innovative Technology solvent drying system saturated withArgon. High-purity polymer grade ethylene was obtained from MathesonTriGas without further purification. The compounds(2-bromophenyl)diphenyl phosphine, (2,6-dibromophenyl)diphenyl phosphineand [Ni(allyl)Cl]₂ were prepared according to literature procedures.

Nickel phosphine phosphonate ester complexes were readily obtainedthrough the synthetic sequence shown in Scheme 3, FIG. 19. Lithiation of(2-bromophenyl)-bis(2-methoxyphenyl) or more bulky(2-bromopheny)-bis(2,6-dibromophenyl), followed by reaction withchlorophosphite-PEG₂ (2) provided ligands 3a, and 3b(Ar=2,6-dimethoxyphenyl) in moderate yields.

Preparation of 3b:

A 100 mL Schlenk flask was charged with(2-bromophenyl)bis(2,6-dimethoxyphenyl) phosphine (0.92 g, 2.00 mmol,1.0 equiv.) in 30 mL of THF. The flask was cooled to −78° C., and asolution of n-butyllithium (1.6 M) (1.3 mL, 2.00 mmol, 1.0 equiv.) wasadded via syringe, giving a deep yellow solution that was stirred for 20min. After stirring for 20 min, a solution of 2 (0.64 g, 2.00 mmol, 1.0equiv.) in THF (5 mL) was added by syringe, which turned the solutionpale orange. After stirring for 40 min, the cold bath was removed, andthe flask was allowed to warm up to room temperature overnight whilestirring. The reaction mixture was then concentrated under reducedpressure to afford an yellow solid. The crude product was purified bysilica gel column chromatography (100% ethyl acetate to remove mobileimpurities, followed by ethyl acetate/chloroform/methanol=10:1:1 toelute the product) to yield a colorless oil (0.59 g, 0.88 mmol, 44.2%).¹H NMR (CDCl₃, 400 MHz): δ (ppm)=8.03 (m, 1H), 7.41 (m, 1H), 7.24 (m,1H), 7.18 (t, J_(HH)=8.4 Hz, 2H), 6.44 (dd, J_(HH)=8.6 Hz, J_(PH)=2.8Hz, 4H), 4.15 (m, 2H), 4.06 (m, 2H), 3.54 (m, 4H), 3.46 (m, 8H), 3.40(s, 12H), 3.34 (s, 6H). ¹³C NMR (CDCl₃, 100 MHz): δ (ppm)=162.38 (d,J_(PC)=8.8 Hz), 144.67 (dd, J_(PC)=25.3, 12.7 Hz), 134.67 (d,J_(PC)=15.5 Hz), 133.82 (dd, J_(PC)=10.7, 8.6 Hz), 131.83 (dd,J_(PC)=187.8, 36.0 Hz), 130.58 (d, J_(PC)=2.9 Hz), 129.69, 126.40 (d,J_(PC)=14.6 Hz), 115.34 (d, J_(PC)=23.3 Hz), 104.74, 71.94, 70.34, 70.02(d, J_(PC)=6.8 Hz), 64.51 (dd, J_(PC)=5.8, 2.9 Hz), 59.10, 55.96. ³¹PNMR (CDCl₃, 162 MHz): δ (ppm)=21.12, −40.64. ESI-MS(+) calc. forC₃₂H₄₄O₁₁P₂[M+Na]⁺=689.2256, found 689.2212.

Preparation of 5b:

A 100 mL Schlenk flask was charged with(2-bromophenyl)bis(2,6-dimethoxyphenyl) phosphine (0.8 g, 1.73 mmol, 1.0equiv.) in 30 mL of THF. The flask was cooled to −78° C., and a solutionof n-butyllithium (1.6 M) (1.1 mL, 1.73 mmol, 1.0 equiv.) was added viasyringe, giving a deep yellow solution. After stirring for 20 min, asolution of chlorodiethylphosphate (0.30 g, 1.73 mmol, 1.0 equiv.) inTHF (5 mL) was added by syringe, which turned the solution pale orange.After stirring for 40 min, the cold bath was removed, and the flask wasallowed to warm up to room temperature overnight while stirring. Thereaction mixture was then concentrated under reduced pressure to afforda white solid. The crude product was purified by silica gel columnchromatography (Ethyl acetate/Hexane=7:3) to yield a white solid (0.85g, 1.56 mmol, 53%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=8.09 (m, 1H), 7.42(m, 1H), 7.24 (m, 1H), 7.18 (td, J_(HH)=8.0 Hz, J_(HH)=1.2 Hz, 2H), 6.44(dd, J_(HH)=8.4 Hz, J_(PH)=2.8 Hz, 4H), 4.00 (m, 4H), 3.40 (s, 12H),1.05 (t, J_(HH)=7.2 Hz, 6H). ¹³C NMR (CDCl₃, 100 MHz): δ (ppm)=162.38(d, J_(PC)=8.8 Hz), 144.43 (dd, J_(PC)=25.3, 11.7 Hz), 134.65 (d,J_(PC)=15.6 Hz), 134.02 (dd, J_(PC)=11.2, 8.8 Hz), 132.38 (dd,J_(PC)=185.8, 35.0 Hz), 130.52 (d, J_(PC)=2.9 Hz), 129.56, 126.34 (d,J_(PC)=15.5 Hz), 115.55 (d, J_(PC)=22.4 Hz), 104.72, 61.75 (d,J_(PC)=3.9 Hz), 55.96, 16.07 (d, J_(PC)=5.9 Hz). ³¹P NMR (CDCl₃, 162MHz): δ (ppm)=20.82, −40.40. ESI-MS(+) calc. forC₂₆H₃₂O₇P₂[M+K]⁺=557.1260, found 557.1225.

Metallation of 3 by treatment with [Ni(allyl)Cl]₂ gave the respective Nicomplexes. Subsequent abstraction of chloride using AgSbF₆ furnishedcomplexes 4a and 4b in high yields, as shown in Scheme 4 in FIG. 20. Forcomparative studies, two nickel complexes without PEG chains 6a and 6b,were synthesized using similar procedures.

Preparation of 4a:

Inside the glovebox, a solution containing 3a (200 mg, 0.33 mmol, 1.0equiv.) and AgSbF₆ (113 mg, 0.33 mmol, 1.0 equiv.) in 10 mL of CH₂Cl₂was stirred for 10 min at RT. Solid [Ni(allyl)Cl]₂ (45 mg, 0.16 mmol,0.5 equiv.) was added in small portions. The reaction mixture wasstirred for an additional 3 h. The resulting red mixture was filteredthrough a pipet plug and then dried under vacuum to give a dark red oil.The product was recrystallized by dissolving in CH₂Cl₂ and then layeringwith pentane to afford the final product as dark red oil (289 mg, 0.31mmol, 93.2%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=7.69 (m, 1H), 7.66 (m,1H), 7.56 (m, 3H), 7.14-7.08 (m, 3H), 6.97 (t, J_(HH)=7.8 Hz, 2H), 6.78(m, 2H), 5.71 (m, 1H), 4.05 (m, 2H), 3.99 (m, 2H), 3.87 (s, 6H), 3.52(m, 12H), 3.87 (s, 6H), 2.59 (brs, 1H). ¹³C NMR (CDCl₃, 125 MHz): δ(ppm)=160.73 (d, J_(PC)=7.4 Hz), 134.87 (dd, J_(PC)=35.5, 13.5 Hz),134.55, 134.44 (d, J_(PC)=4.9 Hz), 134.12, 133.74 (t, J_(PC)=14.8 Hz),133.55, 131.09 (d, J_(PC)=13.5 Hz), 127.72 (dd, J_(PC)=188.5, 17.1 Hz),121.75 (d, J_(PC)=8.6 Hz), 115.62, 115.24, 114.66, 111.71 (d, J_(PC)=4.9Hz), 71.79, 70.35, 69.36 (d, J_(PC)=6.1 Hz), 67.58 (d, J_(PC)=6.1 Hz),59.08, 56.06. ³¹P NMR (CDCl₃, 162 MHz): δ (ppm)=23.25 (d, J_(PP)=20.4Hz), −1.97 (d, J_(PP)=20.6 Hz).

Preparation of 4b:

Inside the glovebox, a solution containing 3b (100 mg, 0.15 mmol, 1.0equiv.) and AgSbF₆ (52 mg, 0.15 mmol, 1.0 equiv.) in 10 mL of CH₂Cl₂ wasstirred for 10 min at RT. Solid [Ni(allyl)Cl]₂ (20 mg, 0.08 mmol, 0.5equiv.) was added in small portions. The reaction mixture was stirredfor an additional 3 h. The resulting red mixture was filtered through apipet plug and then dried under vacuum to give a dark red oil. Upon theaddition of pentane and after stirring for ˜5 min, an orange solidformed. The product was recrystallized by dissolving in CH₂Cl₂ and thenlayering with pentane to afford the final product as orange crystals(142 mg, 0.14 mmol, 94.5%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=7.79 (m,1H), 7.57 (m, 1H), 7.49 (m, 2H), 7.44 (t, J_(HH)=8.4 Hz, 2H), 6.60 (dd,J_(HH)=8.2, 4.0 Hz, 4H), 5.66 (m, 1H), 3.95 (m, 2H), 3.84 (m, 2H), 3.64(s, 12H), 3.50 (m, 12H), 3.35 (s, 6H), 2.86 (brs, 2H), 2.30 (d,J_(HH)=13.2 Hz, 2H). ¹³C NMR (CDCl₃, 125 MHz): δ (ppm)=161.53 (d,J_(PC)=2.9 Hz), 138.11 (dd, J_(PC)=40.4, 12.7 Hz), 134.46 (d,J_(PC)=14.6 Hz), 133.78, 133.38 (t, J_(PC)=8.8 Hz), 131.42 (d,J_(PC)=3.9 Hz), 129.59 (d, J_(PC)=13.6 Hz), 124.91 (dd, J_(PC)=184.9,19.5 Hz), 111.86, 105.62, 105.13, 104.57 (d, J_(PC)=3.9 Hz), 71.84,70.40, 69.37 (d, J_(PC)=6.9 Hz), 67.01 (d, J_(PC)=5.8 Hz), 59.08, 55.98.³¹P NMR (CDCl₃, 162 MHz): δ (ppm)=23.58 (d, J_(PP)=25.9 Hz), −21.78 (d,J_(PP)=24.1 Hz). Anal. Calc. for C₃₅H₄₉F₆O₁₁P₂SbNi·0.25CH₂Cl₂: C, 41.37;H, 4.88. Found: C, 41.30; H, 4.95.

Preparation of 6a:

Inside the glovebox, a solution containing 5a (100 mg, 0.22 mmol, 1.0equiv.) and AgSbF₆ (75 mg, 0.22 mmol, 1.0 equiv.) in 10 mL of CH₂Cl₂ wasstirred for 10 min at RT. Solid [Ni(allyl)Cl]₂ (30 mg, 0.11 mmol, 0.5equiv.) was added in small portions. The reaction mixture was stirredfor an additional 3 h. The resulting red mixture was filtered through apipet plug and then dried under vacuum to give a dark red oil. Upon theaddition of pentane and after stirring for ˜5 min, a yellow solidformed. The product was recrystallized by dissolving in CH₂Cl₂ and thenlayering with pentane to afford the final product as yellow crystals(160 mg, 0.20 mmol, 91.6%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=7.85 (m,1H), 7.69 (m, 1H), 7.58 (m, 3H), 7.14-7.08 (m, 3H), 6.98 (t, J_(HH)=7.2Hz, 2H), 6.79 (m, 2H), 5.72 (m, 1H), 3.97 (m, 4H), 3.88 (s, 6H), 2.55(brs, 1H), 1.18 (t, J_(HH)=6.8 Hz, 6H). ¹³C NMR (CDCl₃, 100 MHz): δ(ppm)=160.72 (d, J_(PC)=6.8 Hz), 135.08 (dd, J_(PC)=36.0, 12.6 Hz),134.64 (d, J_(PC)=4.9 Hz), 134.11, 134.02, 133.88 (t, J_(PC)=7.8 Hz),133.55 (dd, J_(PC)=5.8, 2.9 Hz), 131.17 (d, J_(PC)=13.7 Hz), 127.85 (dd,J_(PC)=185.8, 17.6 Hz), 121.72 (d, J_(PC)=8.8 Hz), 115.68, 115.19,114.56, 111.69 (d, J_(PC)=3.9 Hz), 65.20 (d, J_(PC)=6.8 Hz), 56.05,15.91 (d, J_(PC)=6.8 Hz). ³¹P NMR (CDCl₃, 162 MHz): δ (ppm)=22.91 (d,J_(PP)=21.1 Hz), −2.33 (d, J_(PP)=20.6 Hz). Anal. Calc. forC₂₇H₃₃F₆O₅P₂SbNi: C, 40.85; H, 4.19. Found: C, 40.60; H, 4.43.

Preparation of 6b:

Inside the glovebox, a solution containing 5b (100 mg, 0.19 mmol, 1.0equiv.) and AgSbF₆ (66 mg, 0.19 mmol, 1.0 equiv.) in 10 mL of CH₂Cl₂ wasstirred for 10 min at RT. Solid [Ni(allyl)Cl]₂ (26 mg, 0.10 mmol, 0.5equiv.) was added in small portions. The reaction mixture was stirredfor an additional 3 h. The resulting red mixture was filtered through apipet plug and then dried under vacuum to give a dark red oil. Upon theaddition of pentane and after stirring for ˜5 min, an orange solidformed. The product was recrystallized by dissolving in CH₂Cl₂ and thenlayering with pentane to afford the final product as orange crystals(139 mg, 0.16 mmol, 85.9%). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)=7.66 (m,1H), 7.58 (m, 1H), 7.51 (m, 2H), 7.44 (t, J_(HH)=8.4 Hz, 2H), 6.61 (dd,J_(HH)=8.2, 4.4 Hz, 4H), 5.67 (m, 1H), 3.83 (m, 4H), 3.64 (s, 12H), 2.86(brs, 2H), 2.30 (d, J_(HH)=13.2 Hz, 2H), 1.16 (t, J_(HH)=6.8 Hz, 6H).¹³C NMR (CDCl₃, 100 MHz): δ (ppm)=161.54 (d, J_(PC)=2.0 Hz), 138.16 (dd,J_(PC)=40.4, 12.7 Hz), 134.65 (d, J_(PC)=13.6 Hz), 133.79, 132.72 (t,J_(PC)=8.8 Hz), 131.31 (d, J_(PC)=2.9 Hz), 129.63 (d, J_(PC)=14.6 Hz),125.43 (dd, J_(PC)=181.9, 19.4 Hz), 111.78, 105.58, 105.10, 104.56 (d,J_(PC)=2.9 Hz), 64.61 (d, J_(PC)=6.8 Hz), 55.95, 15.88 (d, J_(PC)=6.8Hz). ³¹P NMR (CDCl₃, 162 MHz): δ (ppm)=23.13 (d, J_(PP)=24.6 Hz), −21.86(d, J_(PP)=24.6 Hz). Anal. Calc. for C₂₉H₃₇F₆O₇P₂SbNi: C, 40.79; H,4.37. Found: C, 37.98; H, 4.39.

Single crystals of compounds 4a-Na, 4b-Na and 6a were analyzed by X-raycrystallography. In all three structures, the nickel center is squareplanar, similar to that of other nickel complexes reported previously.The dinuclear structure of the nickel-sodium complex 4a-Na was confirmedby X-ray crystallographic analysis. The structure declared that thenickel center in 4a-Na has the expected square planar geometry, andsodium ion is four-coordinate due to ligation by four oxygen donors fromtwo PEG chians. The Ni—Na bond distance is ˜6.68 Å.

EXAMPLE 11. METAL BINDING STUDIES

NMR spectra were acquired using JEOL spectrometers (ECA-400, 500, and600) and referenced using residual solvent peaks. All ¹³C NMR spectrawere proton decoupled. ³¹P NMR spectra were referenced to phosphoricacid. For polymer characterization: ¹H NMR spectroscopy: each NMR samplecontained ˜20 mg of polymer in 0.5 mL of 1,1,2,2-tetrachloroethane-d₂(TCE-d₂) and was recorded on a 500 MHz spectrometer using standardacquisition parameters at 120° C. ¹³C NMR spectroscopy: Each NMR samplecontained ˜50 mg of polymer and 50 mM (8.7 mg) chromium acetylacetonateCr(acac)₃ in 0.5 mL of TCE-d₂ and was recorded at 120° C. (125 MHz). Thesamples were acquired using a 90° pulse of 11.7 μs, a relaxation delayof 4 s, an acquisition time of 0.81 s, and inverse gated decoupling. Thesamples were preheated for 30 mM prior to data acquisition. The carbonspectra were assigned based on the chemical shift values reported in theliterature. High-resolution mass spectra were obtained from themassspectral facility at the University of Houston. Elemental analyseswere performed by Atlantic Microlab. Gel permeation chromatography (GPC)data were obtained using a Malvern high temperature GPC instrumentequipped with refractive index, viscometer, and light scatteringdetectors at 160° C. with 1,2,4-trichlorobenzene (stabilized with 125ppm BHT) as the mobile phase. A calibration curve was established usingpolystyrene standards in triple detection mode. All molecular weightsreported are based on triple detection.

The method of continuous variation (Job Plot analysis) was used todetermine the binding stoichiometry of our nickel complexes with alkaliions. To investigate the interactions of the PEGylated nickel compoundswith alkali ions, solution studies were carried out in chloroform-d. Toperform these experiments, stock solutions of 4a (or 4b) (6 mM, 6 mL)and MBAr^(F) ₄ (6 mM, 15 equiv. Et₂O to solubilize the salts, 6 mL,M=Li⁺, Na⁺, or K⁺) were prepared separately in CDCl₃. Various amounts ofeach stock solution were added to an NMR tube so that a total volume of1 mL was obtained. Ten different NMR samples were prepared, eachcontaining a different ratio of 4a (or 4b):M. NMR spectra of 4a and 4bin the presence of various amounts of MBAr^(F) ₄ salts (M=Li⁺, Na⁺, orK⁺; BAr^(F) ₄=tetrakis(3,5-trifluoromethylphenyl)borate) were recorded.The samples were recorded at room temperature by ¹H NMR spectroscopy.The hydrogen resonances centered at both 4a (˜5.72 ppm) and 4b (˜5.67ppm) shift in the presence of sodium ions. It was observed that theH_(a) from allyl group of both 4a (˜5.72 ppm) and 4b (˜5.67 ppm) showedgreater chemical shifts when larger amounts of M⁺ were present. Thechanges in the chemical shifts of H_(a) were used to construct Jobplots, shown in FIG. 21.

FIG. 21 shows Job plots for complex 4a with NaBAr^(F) ₄ (circles) and 4bwith NaBAr^(F) ₄ (triangles)) in CDCl₃. The total concentration of4a-b/Na was 6 mM for all data points. The peak maxima of the Job plotsfor 4a/Na⁺ and 4b/Na⁺ all occur at X_(Ni)=0.5, which indicates that a1:1 stoichiometry is optimal between complex 4a or 4b with alkali ions.The slopes of the two plots suggest 4a has a higher affinity for sodiumthan 4b. Interestingly, complex 6a also shows chemical shift in its NMRspectra when 1 equiv. sodium salt was added. These data are consistentwith previous observations that palladium complexes lacking PEG chainsare capable of forming adducts with sodium.

To determine whether other metal ions are capable of binding, job plotstudies of 4a were performed with zinc triflate to determine the bindingstoichiometry of the nickel complexes with zinc ions. The experiment wascarried out in acetonitrile-d to ensure that zinc triflate salt wascompletely dissolved. To perform these experiments, stock solutions of4a (6 mM, 6 mL) and Zn(OTf)₂ (6 mM, 6 mL) were prepared separately inCD₃CN. Various amounts of each stock solution were added to an NMR tubeso that a total volume of 1 mL was obtained. Ten different NMR sampleswere prepared, each containing a different ratio of 4a:Zn. The hydrogenresonances centered at ˜5.7 ppm corresponding to the carbon #32 of allylgroup in 4a shift in the presence of zinc ions. It was observed thatH_(a) from the allyl group of 4a (˜5.72 ppm was shifted downfield whenlarger amounts of Zn²⁺ were present. These data were used to construct aJob plot of Zn²⁺ binding to 4a, shown in FIG. 22. FIG. 22 shows the Jobplot for complex 4a with Zn(OTf)₂ (black circles) in CD₃CN. The totalconcentration was 6 mM for all data points. The peak maximum of the Jobplot for 4a/Zn²⁺ occurred at X_(Ni)=0.5, which suggests that a 1:1stoichiometry between Ni/Zn is optimal. When Zn(OTf)₂ was added to 6a,the spectrum showed several new peaks that we were unable to assign.However, based on their relative peak integration, zinc binding to 6adoes not appear to form a single discrete heterobimetallic complex. Thisobservation is consistent with polymerization studies described belowwhich showed that the addition of Zn²⁺ did not improve the activity of6a.

EXAMPLE 12. POLYMERIZATION STUDIES

Nickel phosphine phosphonate PEG complexes 4a/4b, and Jordan-type 6a/6bwere tested as catalysts for ethylene homopolymerization. Inside thedrybox, the nickel complexes (10 μmol) and alkali salts (10 μmol) weredissolved in 10 mL of toluene/DCM (8:2) and stirred for 10 mins. Byvisual inspection, the resulting nickel-alkali complexes appeared to besoluble in the reaction mixture. The mixture was sealed inside a vialusing a rubber septum and brought outside of the drybox. Under anatmosphere of N₂, the catalyst solution was loaded into a syringe. Toprepare the polymerization reactor, 40 mL of dry toluene was added to anempty autoclave and preheated to the desired temperature. The autoclavewas purged with ethylene (20 psi) for 1 min and then the catalystsolution was injected into the autoclave via syringe. The reactorpressure was increased to 200 psi of ethylene and the contents werestirred vigorously for 1 h. To stop the polymerization, the autoclavewas vented and cooled in an ice bath. A solution of MeOH (100-200 mL)was added to precipitate the polymer. The polymer was collected byvacuum filtration, rinsed with MeOH, and dried under vacuum at 80° C.overnight. The reported yields are average values of triplicate runs.Results are shown in Table 11 below.

TABLE 11 Ethylene Homopolymerization Activity Com- Polymer (10⁵ g/Branches^(c) M_(n) ^(d) M_(w)/ Entry plex Salt Yield (g) mol · h) (/1000C) (×10³) M_(n) ^(d) 1 4a none 8.6 8.6 22 0.84 1.7 2 4a Na⁺ 29.9 29.9 301.04 1.2 3^(b) 4b none 6.1 3.0 13 4.79 1.4 4^(b) 4b Na⁺ 3.5 1.8 16 7.611.4 5 6a none 7.4 7.4 18 0.69 1.7 6 6a Na⁺ 26.6 26.6 26 0.98 2.0 7^(b)6b none 5.4 2.7 17 7.36 1.2 8^(b) 6b Na⁺ 3.3 1.6 15 13.92 1.3^(a)Polymerization conditions: Ni catalyst (10 μmol), NaBAr^(F) ₄ (10μmol), ethylene (200 psi), 2 mL DCM, 48 mL toluene, 1 h at 80° C.^(b)Polymerization conditions: Ni catalyst (20 μmol), NaBAr^(F) ₄ (20μmol), ethylene (400 psi). ^(c)The total number of branches per 1000carbons was determined by ¹H NMR spectroscopy. ^(d)Determined by GPC intrichlorobenzene at 150° C.

It was found that at 80° C. in toluene under 200 psi (400 psi for 4b and6b) of ethylene, all nickel complexes showed high activity (2.7˜8.6×10⁵g/mol Ni·h). 4a and 4b showed slightly higher activity than 6a and 6b,respectively (Table 11, entry 1 vs. 5 and entry 3 vs. 7). Interestingly,the complexes 4a and 6a containing 2-methoxyphenyl groups were much moreactive than those containing 2,6-dimethoxypheny group (4b and 6b). Onthe other hand, the bulkier catalysts gave PE with higher molecular(M_(n)=˜4.79-7.36×10³) than that obtained using the less bulky catalysts(M_(n)=˜0.69-0.84×10³) (Table 11, entry 1 vs. 3 and entry 5 vs. 7).These results are consistent with other reported Ni systems, in whichmore sterically hindered catalysts exhibited reduced catalyst activityin favor of higher molecular weight polymers compared to less bulkycatalysts. In all cases, the polymers produced contained moderatebranches (20 branches or less per 1000 carbons).

Next, the effects of alkali salts on the catalyst's reactivity towardethylene were evaluated (Table 11, entries 2, 4, 6, 8). It was observedthat the reaction of 4a or 6a with NaBAr^(F) ₄ (1:1) led to catalyticrate enhancements of about 3.5×, 3.6× respectively (entries 2 and 4),compared to their mononickel complexes. The polymer molecular weight andpolydispersity remained relatively constant in both the presence andabsence of alkali ions. In contrast, complexes 4b and 6b showed slightlydecreased activity when alkali salts were added (entries 4 and 8), butthe polymer molecular weight increased. The alkali salts LiBAr^(F) ₄ andKBAr^(F) ₄ were also tested in polymerization, and similar results wereobtained. As shown above, the reaction of 4a+Na and 4b+Na both gaveheterobimetallic species. However, because the sodium ions do notcoordinate to the P═O oxygen donor, their binding to the nickelcomplexes only increases the steric bulk and does not alter theelectronic structure of the catalysts. Thus, differences inpolymerization due to the presence of alkali ions may be due primarilyto steric effects.

Complexes 4a and 6a were chosen for further studies using a polarsolvent, with results shown in Table 12 below.

TABLE 12 Ethylene Homopolymerization in THF/Toluene Mixture SolventSolvent Activity Branches^(b) M_(n) ^(c) M_(w)/ Entry Complex Salt(THF/Toluene) (10⁵ g/mol · h) (/1000 C) (×10³) M_(n) ^(c) 1 4a none 0/50 8.6 22 0.84 1.7 2 4a none  2/48 8.7 21 1.14 1.6 3 4a none 10/406.8 19 0.86 1.3 4 4a none 50/0  2.5 21 0.70 1.1 5 4a K⁺  0/50 28.9 281.12 1.2 5 4a K⁺  2/48 28.7 32 0.84 1.7 6 4a K⁺ 10/40 30.9 31 0.77 2.2 74a K⁺ 50/0  7.5 24 0.83 1.9 8 4a Na⁺ 50/0  6.1 24 0.95 1.2 9 6a none 0/50 7.4 18 0.69 1.7 10 6a none  2/48 4.1 16 1.64 1.2 11 6a none 10/407.5 17 0.78 1.5 12 6a none 50/0  2.5 19 0.90 1.2 13 6a K⁺  0/50 25.4 220.73 1.7 14 6a K⁺  2/48 21.9 24 0.87 1.6 15 6a K⁺ 10/40 36.3 27 0.61 1.616 6a K⁺ 50/0  6.6 21 0.95 1.2 17 6a Na⁺ 50/0  6.5 19 1.01 1.7^(a)Polymerization conditions: Ni catalyst (10 μmol), MBAr^(F) ₄ (10μmol), ethylene (200 psi), 50 ml toluene and THF in different ratios, 1h at 80° C. ^(b)The total number of branches per 1000 carbons wasdetermined by ¹H NMR spectroscopy. ^(c)Determined by GPC intrichlorobenzene at 150° C.

It was found that the activities of 4a and 6a were relatively constantin the presence of up to ˜20% of THF in toluene (entries 2 vs 3; 5 vs 6;10 vs 11; 14 vs 15). However, when polymerizations were carried out inneat THF, the activity of 4a dropped at least 3× compared to that inneat toluene (entries 1 vs 4; 5 vs 7). The Jordan-type complex 6aexhibited similar behavior as that of 4a (entries 9 vs 12; 13 vs 16).Although the addition of polar solvent reduces catalyst activity asexpexted,^(12,13) our nickel complex 4a is still highly active in thepresence of alkali ions (7.5×10⁵ g/mol NH) for Ni·K and 6.1×10⁵ g/molNi·h for Ni+Na). Interestingly, polymerizations performed in THF gave PEwith the same microstructure as that obtained using toluene. Thepolymers have low molecular weights (M_(n)=˜0.61-1.64×10³) with narrowpolydispersities (PDI=˜1.2-2.2).

Since the Ni catalysts are active in the polar solvent THF,polymerizations were studied in the presence of metals salts that werenot soluble in toluene. Polymerization reactions were carried out under200 psi of ethylene using 4a or 6a and 1 equiv. of a triflate salt inneat THF, with the results shown in Table 13 below.

TABLE 13 Ethylene Homopolymerization with Metal Triflates in THFActivity Com- Polymer (10⁵ g/ Branches^(b) M_(n) ^(c) M_(w)/ Entry plexSalt Yield (g) mol · h) (/1000 C) (×10³) M_(n) ^(c) 1 4a Zn²⁺ 12.1 12.127 0.84 1.2 2 4a Mg²⁺ 6.2 6.2 23 0.86 1.8 3 4a Ca²⁺ 7.7 7.7 24 0.98 1.24 4a La³⁺ 5.2 5.2 25 0.66 1.4 5 4a Sc³⁺ 3.7 3.7 22 0.62 1.3 6 4a Ga³⁺5.5 5.5 18 0.79 2.1 7 4a Co²⁺ 26.6 26.6 18 0.91 1.8 8 6a Zn²⁺ 2.5 2.5 190.87 2.2 9 6a Mg²⁺ 3.2 3.2 19 0.76 1.5 10 6a Ca²⁺ 2.8 2.8 19 0.77 1.7 116a La³⁺ 2.1 2.1 19 0.76 1.2 12 6a Sc³⁺ 2.0 2.0 20 0.68 1.6 13 6a Ga³⁺2.4 2.4 19 0.79 1.3 14 6a Co²⁺ 1.9 1.9 22 0.99 2.3 ^(a)Polymerizationconditions: Ni catalyst (10 μmol), M(OTf)_(n) (10 μmol), ethylene (200psi), 50 mL THF, 1 h at 80° C. ^(b)The total number of branches per 1000carbons was determined by ¹H NMR spectroscopy. cDetermined by GPC intrichlorobenzene at 150° C.

All of the triflate salts dissolved completely in the THF when mixedwith the nickel complexes. For catalysts 4a and 6a, the addition of K⁺or Na⁺ did not significantly change their activities (7.5×10⁵ vs.6.6×10⁵ g/mol Ni·h, 6.1×10⁵ vs. 6.5×10⁵ g/mol Ni·h, respectively) (Table12, entries 7, 8, 16, 17). However, when other triflate salts such asZn²⁺, Mg²⁺, Ca²⁺, Co²⁺, La³⁺, Sc⁺, Ga⁺ were added under the samecondition, 4a showed increased catalysts activity but not 6a (Table 13entries 1-7 vs. entries 8-14). FIG. 23 shows a comparison of theactivities of catalysts 4a, 6a with different metal ions. These resultssuggest that the PEG chains are critical to secondary metal ion bindingin THF. An intriguing observation we made was that different metal ionsenhanced the catalyst activity to different extent. For example,combining 1 equiv. of Co²⁺ with 4a led to about 10-fold increase inactivity (Table 12 entry 4 vs. Table 13 entry 7). The most modestcatalyst enhancement was achieved using Sc³⁺ (entry 5).

Besides metal triflates, other metals salts were also tested with 4a.Although ZnCl₂ provided high catalyst activity 16.8×10⁵ g/mol Ni·h, allof the other halide salts gave reduced or no polymer yield. It isbelieved that halide anions could bridge multiple metal ions and formhigher nuclearity species that are catalytically inactive.

Due to their remarkable catalyst enhancing effects, cobalt and zinctriflate were further studied as additivities in the copolymerization ofethylene and polar monomers in THF at 80° C. Inside the drybox, thenickel complexes (40 μmol) and metal triflate (40 μmol) were dissolvedin 10 mL of THF and stirred for 10 mins. The mixture was sealed inside avial using a rubber septum and brought outside of the drybox. To preparethe polymerization reactor, 35-37 mL of dry THF was added to an emptyautoclave and preheated to the desired temperature. The autoclave waspurged with ethylene (20 psi) for 1 min and then the polar comonomer wasadded first, followed with the catalyst solution was injected into theautoclave via syringe. The reactor pressure was increased to 400 psi ofethylene and the contents were stirred vigorously for 2 h. To stop thepolymerization, the autoclave was vented and cooled in an ice bath. Asolution of MeOH (100-200 mL) was added to precipitate the polymer. Thepolymer was collected by vacuum filtration, rinsed with MeOH, and driedunder vacuum at 80° C. overnight. The reported yields are average valuesof triplicate runs, with results shown in Table 14 below.

TABLE 14 Ethylene Comopolymerization for 4a with metal triflates in THFActivity C(M) (kg/mol · Branches^(c) Inc M_(n) ^(d) M_(w)/ Entry SaltComonomer (mol/L) h) (/1000 C) (%) (×10³) M_(n) ^(d)  1 — PVE 1.0 6.9 210.21 1.43 1.2  2 Co(OTF)₂ PVE 1.0 34.2 25 0.21 1.29 1.3  3 Zn(OTF)₂ PVE1.0 16.8 27 0.24 1.14 2.2  4 KBAr^(F) ₄ PVE 1.0 7.6 23 0.25 1.26 1.8 5^(e) Co(OTF)₂ PVE 1.0 0 — — — —  6 — ABE 0.5 <0.1 — — — —  7 Co(OTF)₂ABE 0.5 1.9 23 0.21 5.06 2.4  8 Zn(OTF)₂ ABE 0.5 1.0 25 0.33 1.50 1.5 9^(b) _ MUD 0.5 14.5 20 0.38 1.61 1.3 10^(b) Co(OTF)₂ MUD 0.5 73.5 230.69 2.15 1.5 11^(b) Zn(OTF)₂ MUD 0.5 61.0 23 0.74 1.94 1.3 12 — AP 0.59.1 21 0.31 2.23 1.6 13 Co(OTF)₂ AP 0.5 68.1 28 0.20 1.78 1.4 14Zn(OTF)₂ AP 0.5 27.1 21 0.29 1.82 1.2 15 — MA 1.0 0 — — — — 16 Co(OTF)₂MA 1.0 0 — — — — ^(a)Polymerization conditions: Ni catalyst (40 μmol),M(OTF)₂ (40 μmol), ethylene (400 psi), 50 mL THF, 2 h at 80° C.^(b)Polymerization conditions: Ni catalyst (20 μmol), M(OTF)₂ (20 μmol).^(c)The total number of branches per 1000 carbons was determined by ¹HNMR spectroscopy. ^(d)Determined by GPC in trichlorobenzene at 150° C.^(e)In the absence of 4a.

The nickel complexes could not copolymerize polar monomers such as MA(methyl acrylate), VA (Vinyl acetate), AA (allyl acetate) (entry 15,16).However, the catalysts were capable of copolymerizing PVE (propyl vinylether), ABE (allyl butyl ether), methyl 10-undecenoate (MUD) and4-pentenyl acetate (AP). The reaction of 4a with ethylene/PVE at 80° C.afforded poly(ethylene-co-propyl vinyl ether) containing ˜0.2 mol % ofin-chain polar groups (entry 1). Under similar polymerizationconditions, the 4a-M complexes also furnished copolymers with lowmolecular weight (10³) and low incorporation ˜0.2 mol % (entries 2,3).Consistent with the ethylene homopolymerization studies above, theheterobimetallic complexes Ni—M were more active than their mononickelcounterparts. The highest activity was using 4a-Co, which gave about a5.0× improvement over that of the 4a complex itself (entry 1 vs. 2). Ina comparison, 4a-K only gave a 1.1× increase in copolymerizationactivity (entry 4).

When the double bond and the polar groups were separated by long carbonchains, these monomers could be copolymerized with good catalystactivity and gave polymers with modest comonomer incorporation. Forexample, the copolymerization of ethylene with methyl 10-undecenoate(MUD) using 4a-Co and 4a-Zn provided catalysts activities of 73.5×10³and 61.0×10³ g/mol Ni·h, respectively (entries 10,11). FIG. 24 shows acomparison of the activities of catalysts 4a, 4a-Zn, 4a-Co withdifferent polar monomers. As FIG. 24 clearly shows, the heterobimetalliccomplexes were faster catalysts than the mononickel complexes for theseselect polar monomers.

Since cobalt ions could potentially induce cationic or radicalpolymerization to give homopoly(PVE), addition control studies wereconducted. To confirm that 4a is needed to obtain copolymers of ethyleneand PVE, polymerizations were carried out using just Co(OTf)₂ and no 4a(entry 14). As expected, no polymer had formed. Interestingly, whencopolymerization was performed in toluene instead of THF, the activitydidn't change much. For example, the copolymerization of ethylene withPVE in toluene gave an activity of 6.7×10³ g/mol Ni·h, which is similarto that in THF (compare entry 1). This result is unexpected becauseethylene homopolymerization is significantly suppressed in polarsolvents compared to in nonpolar solvents. In copolymerization, thepolar monomers are likely more coordinating than THF so the solvent hasminimal effect on catalyst activity. Palladium catalysts are typicallymore active than nickel catalysts in the copolymerization ofethylene/olefin ethers. The 4a-Co catalyst is the exception to thistrend. Here, the copolymer molecular weight and incorporation ratioswere relatively low. According to the X-ray structure of 4a-Na, the twometals are two far apart to engage in cooperative reactivity. Since thesecondary ion does not have any electronic effect on the nickel center,it is believed that its presence only increases the steric bulk of thecatalyst.

REFERENCES

-   The references listed below are, to the extent permissible,    incorporated by reference herein in their entireties.-   Klosin, J.; Fontaine, P. P.; Figueroa, R. Acc. Chem. Res. 2015, 48,    2004-2016.-   Chung, T. C. M. Functionalization of Polyolefins; Academic Press:    San Diego, Calif., 2002.-   Xie, T.; McAuley, K. B.; Hsu, J. C. C.; Bacon, D. W. Ind. Eng. Chem.    Res. 1994, 33, 449-479.-   Johnson, L. K.; Mecking, S.; Brookhart, M. J. Am. Chem. Soc. 1996,    118, 267-268.-   Boffa, L. S.; Novak, B. M. Chem. Rev. 2000, 100, 1479-1493.-   Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. Rev. 2000, 100,    1169-1203.-   Nakamura, A.; Anselment, T. M. J.; Claverie, J.; Goodall, B.;    Jordan, R. F.; Mecking, S.; Rieger, B.; Sen, A.; van    Leeuwen, P. W. N. M.; Nozaki, K. Acc. Chem. Res. 2013, 46,    1438-1449.-   Nakamura, A.; Ito, S.; Nozaki, K. Chem. Rev. 2009, 109, 5215-5244.-   Chen, C. Nat. Rev. Chem. 2018, 2, 6-14.-   Radlauer, M. R.; Buckley, A. K.; Henling, L. M.; Agapie, T. J. Am.    Chem. Soc. 2013, 135, 3784-3787.-   Drent, E.; van Dijk, R.; van Ginkel, R.; van Oort, B.; Pugh, R. I.    Chem. Commun. 2002, 744-745.-   Ito, S.; Munakata, K.; Nakamura, A.; Nozaki, K. J. Am. Chem. Soc.    2009, 131, 14606-14607.-   Wada, S.; Jordan, R. F. Angew. Chem., Int. Ed. Engl. 2017, 56,    1820-1824.-   Weng, W.; Shen, Z.; Jordan, R. F. J. Am. Chem. Soc. 2007, 129,    15450-15451.-   Kochi, T.; Noda, S.; Yoshimura, K.; Nozaki, K. J. Am. Chem. Soc.    2007, 129, 8948-8949.-   Friedberger, T.; Wucher, P.; Mecking, S. J. Am. Chem. Soc. 2012,    134, 1010-1018.-   Carrow, B. P.; Nozaki, K. J. Am. Chem. Soc. 2012, 134, 8802-8805.-   Carrow, B. P.; Nozaki, K. Macromolecules 2014, 47, 2541-2555.-   Contrella, N. D.; Sampson, J. R.; Jordan, R. F. Organometallics    2014, 33, 3546-3555.-   Chen, M.; Chen, C. Angew. Chem., Int. Ed. Engl. 2018, 57, 3094-3098.-   Younkin, T. R.; Connor, E. F.; Henderson, J. I.; Friedrich, S. K.;    Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460-462.-   Cai, Z.; Xiao, D.; Do, L. H. J. Am. Chem. Soc. 2015, 137,    15501-15510.-   Cai, Z.; Do, L. H. Organometallics 2017, 36, 4691-4698.-   Smith, A. J.; Kalkman, E. D.; Gilbert, Z. W.; Tonks, I. A.    Organometallics 2016, 35, 2429-2432.-   Renny, J. S.; Tomasevich, L. L.; Tallmadge, E. H.; Collum, D. B.    Angew. Chem., Int. Ed. Engl. 2013, 52, 11998-12013.-   Smith, J. B.; Kerr, S. H.; White, P. S.; Miller, A. J. M.    Organometallics 2017, 36, 3094-3103.-   Dudkina, Y. B.; Kholin, K. V.; Gryaznova, T. V.; Islamov, D. R.;    Kataeva, O. N.; Rizvanov, I. K.; Levitskaya, A. I.; Fominykh, O. D.;    Balakina, M. Y.; Sinyashin, O. G.; Budnikova, Y. H. Dalton Trans.    2017, 46, 165-177.-   Therrien, J. A.; Wolf, M. O.; Patrick, B. O. Inorg. Chem. 2014, 53,    12962-12972.-   Brown, I. D.; Skowron, A. J. Am. Chem. Soc. 1990, 112, 3401-3403.-   Delgado, M.; Ziegler, J. M.; Seda, T.; Zakharov, L. N.;    Gilbertson, J. D. Inorg. Chem. 2016, 55, 555-557.-   Ma, Z.; Yang, W.; Sun, W.-H. Chin. J. Chem. 2017, 35, 531-540.-   Rhinehart, J. L.; Brown, L. A.; Long, B. K. J. Am. Chem. Soc. 2013,    135, 16316-16319.-   Rhinehart, J. L.; Mitchell, N. E.; Long, B. K. ACS Catal. 2014, 4,    2501-2504.-   Ikeda, S.; Ohhata, F.; Miyoshi, M.; Tanaka, R.; Minami, T.; Ozawa,    F.; Yoshifuji, M. Angew. Chem., Int. Ed. Engl. 2000, 39, 4512-4513.-   Kim, T.-J.; Kim, S.-K.; Kim, B.-J.; Hahn, J. S.; Ok, M.-A.; Song, J.    H.; Shin, D.-H.; Ko, J.; Cheong, M.; Kim, J; Won, H.; Mitoraj, M.;    Srebro, M.; Michalak, A.; Kang, S. O. Macromolecules 2009, 42,    6932-6943.-   Biernesser, A. B.; Li, B.; Byers, J. A. J. Am. Chem. Soc. 2013, 135,    16553-16560.-   Broderick, E. M.; Guo, N.; Vogel, C. S.; Xu, C.; Sutter, J.;    Miller, J. T.; Meyer, K.; Mehrkhodavandi, P.; Diaconescu, P. L. J.    Am. Chem. Soc. 2011, 133, 9278-9281.-   Zhang, F.; Wang, L.; Chang, S.-H.; Huang, K.-L.; Chi, Y.; Hung,    W.-Y.; Chen, C.-M.; Lee, G.-H.; Chou, P.-T., Dalton Trans. 2013, 42,    7111-7119.-   Rulke, R. E.; Ernsting, J. M.; Spek, A. L.; Elsevier, C. J.; van    Leeuwen, P. W. N. M.; Vrieze, K., Inorg. Chem. 1993, 32, 5769-5778.-   Daugulis, O.; Brookhart, M.; White, P. S., Organometallics 2002, 21,    5935-5943.-   Xin, B. S.; Sato, N.; Tanna, A.; Oishi, Y.; Konishi, Y.; Shimizu,    F., J. Am. Chem. Soc. 2017, 139, 3611-3614.-   Mokhadinyana, M. S. M., Munaka Christopher; Mogorosi, Moses    Mokgolela; Overett, Matthew James; Van den Berg, Jan-Albert; Janse    Van Rensburg, Werner; Blann, Kevin, Patent 2014.-   Reisinger, C. M.; Nowack, R. J.; Volkmer, D.; Rieger, B., Dalton    Trans. 2007, 272-278.-   Acharya, J.; Gupta, A. K.; Shakya, P. D.; Kaushik, M. P.,    Tetrahedron Lett. 2005, 46, 5293-5295.-   Contrella, N. D.; Sampson, J. R.; Jordan, R. F., Organometallics    2014, 33, 3546-3555.-   Smith, J. B.; Kerr, S. H.; White, P. S.; Miller, A. J. M.,    Organometallics 2017, 36, 3094-3103.-   Gates, D. P.; Svejda, S. A.; Oñate, E.; Killian, C. M.; Johnson, L.    K.; White, P. S.; Brookhart, M. Macromolecules 2000, 33, 2320-2334.-   Zhou, X.; Bontemps, S.; Jordan, R. F. Organometallics 2008, 27,    4821-4824.-   Delferro, M.; McInnis, J. P.; Marks, T. J. Organometallics 2010, 29,    5040-5049.-   Kenyon, P.; Wörner, M.; Mecking, S. J. Am. Chem. Soc. 2018, 140,    6685-6689.-   Zhang, Y.; Mu, H.; Pan, L.; Wang, X.; Li, Y. ACS Catal. 2018, 8,    5963-5976.-   Noda, S.; Kochi, T.; Nozaki, K. Organometallics 2009, 28, 656-658.-   Kocen, A.; Brookhart, M.; Daugulis, O. Nature Commun. 2019.-   Cai, Z.; Do, L. H. Organometallics 2018, 37, 3874-3882.-   Brookhart, M.; Grant, B.; Volpe, A. F., Jr. Organometallics 1992,    11, 3920-3922.-   Hirose, K. J. Incl. Phenom. Marocycl. Chem. 2001, 39, 193-209.-   Zhang, Y.-P.; Li, W.-W.; Li, B.-X.; Mu, H.-L.; Li, Y.-S. Dalton    Trans. 2015, 44, 7382-7394.

What is claimed is:
 1. A heterobimetallic catalyst having a structureselected from:

wherein Ar is Ph, (2,6-dimethoxy)Ph or (2-MeO)Ph, Ph is a phenyl group,PPh₃ is triphenylphosphine, PMe₃ is trimethylphosphine, M is Li, Na, orK, R is an alkyl or aryl group, and X is an electron donating orwithdrawing group.
 2. A method for catalyzing homopolymerization ofethylene, comprising: combining ethylene with the heterobimetalliccatalyst of claim 1, whereby the ethylene undergoes homopolymerization.3. A method for catalyzing copolymerization of ethylene and polarolefins, comprising: combining ethylene and polar olefins with theheterobimetallic catalyst of claim 1, whereby the ethylene and polarolefins undergo copolymerization.
 4. A heterobimetallic catalyst havinga structure of:

wherein Ph is a phenyl group and PMe₃ is trimethylphosphine.
 5. A methodfor catalyzing homopolymerization of ethylene, comprising: combiningethylene with the heterobimetallic catalyst of claim 4, whereby theethylene undergoes homopolymerization.
 6. A method for catalyzingcopolymerization of ethylene and polar olefins, comprising: combiningethylene and polar olefins with the heterobimetallic catalyst of claim4, whereby the ethylene and polar olefins undergo copolymerization.
 7. Aheterobimetallic catalyst having a structure selected from:

wherein Ar is an aromatic group, Ph is a phenyl group, PPh₃ istriphenylphosphine, PMe₃ is trimethylphosphine, M is Li, Na, or K, R isan alkyl or aryl group, and X is an electron donating or withdrawinggroup.
 8. A method for catalyzing homopolymerization of ethylene,comprising: combining ethylene with the heterobimetallic catalyst ofclaim 7, whereby the ethylene undergoes homopolymerization.
 9. A methodfor catalyzing copolymerization of ethylene and polar olefins,comprising: combining ethylene and polar olefins with theheterobimetallic catalyst of claim 7, whereby the ethylene and polarolefins undergo copolymerization.